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%  SNO-ARC Science Subcommittee Report for December 1999 Meeting
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%  Versions
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%	0.1  12/12/99  Initial framework distributed to committee
%	0.2  14/12/99  Add Ed Kearns to list
%	0.9  15/12/99  Incorporate all the first drafts
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\begin{document}
\title{The 1999 NSERC and SNO-ARC Science Review of SNO \\
{\small Version 0.9}}
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\maketitle
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\section*{Executive Summary - PKS/MV}

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%  To be written
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\section{Introduction PKS/MV}
%
The NSERC Subatomic Physics Grant Selection Committee (GSC 19) and SNO
Agency Review Committee (SNO-ARC) commissioned independent reviews of the
Sudbury Neutrino Observatory (SNO) in fall 1999.  The NSERC review
follows on similar annual reviews that have been arranged by GSC 19 in
the context of the project grant renewals for the Canadian SNO
collaborators.  The recently reactivated SNO-ARC also established a
Science Subcommittee that was mandated to give advice to both SNO-ARC and
SNO on the science and management of the project.  The memberships of
the two committees are listed in Appendices B and C.

These two committees coordinated their reviews so that a common set of
presentations by SNO collaborators were made to both committees on 8
December 1999. The committees then split up on December 9 for
presentations on funding (GSC committee) and more detailed discussions
on specific issues such as calibration and the long range plan
(SNO-ARC subcommittee).  The agenda for the two-day review is provided in
Appendix D.  A common set of recommendations on scientific and
technical matters was arrived at by the two committees, and so this
report documents the findings of the review.  In the case of the NSERC
review, Appendix A of this report details the committee's funding
recommendations to GSC 19.

The committees wish to thank the SNO collaborators and NSERC staff for
arranging a productive two-day review.  In the opinion of the two
committees, the needs of an NSERC GSC review and the SNO-ARC Science
Subcommittee review have such a large overlap that a more efficient
process could be established.  Since the SNO-ARC Science Subcommittee
is an ongoing one, it is suggested that this committee be augmented by
two GSC members to perform the funding review in the future.

\section{The Science - FH/EK/EB}
%
A series of experiments, covering almost three decades of neutrino
observations of the sun, have established an electron neutrino
($\nu_e$) flux of about half the value calculated.  The set of
available data cannot easily be reconciled with standard solar model (SSM)
calculations because they are incompatible with the existence of the
so-called $^7$Be neutrinos.  Moreover, the SSM appears robust from the
theoretical point of view and have been confirmed by helioseismology
studies.  Therefore, the assumption has been
that the solution to the ``solar neutrino problem'' resides with the
particle physics of the neutrino, and not with the astrophysics of the
sun.  SNO has the potential to reveal the properties of neutrinos
responsible for the deficit in flux, with oscillations providing the best
motivated explanation.  The prospect that SNO provides the first
conclusive evidence for $\nu_e$\ oscillations has been reinforced by the
recent indirect observations of $\nu_\mu$\ oscillations in the atmospheric
neutrino flux.

In the last year, the results from the competing SuperKamiokande
experiment show that that it will be more difficult than expected for
this experiment to provide an unambiguous solution to the solar neutrino
problem.  Their much larger detector has made impressive observations of
the solar neutrino flux confirming, once more, the
$\nu_e$\ deficit.  It does not have the capabilities, however, to
establish the origin of the deficit with good statistical significance. 
Hints provided by measurements of the time- and energy-dependence of the
solar neutrino flux have not converged on a particular solution to the
problem.  SNO has the tools to step in and resolve the solar neutrino
problem over the three year timeframe discribed in its current scientific
plan.  While new detectors such as Borexino will be commissioned during
this time, they are unlikely to be ready to compete.  In any case, data
from all the presently running experiments (SNO, SuperKamiokande, GNO and
SAGE), which detect neutrinos with different energy thresholds and are
therefore sensitive to different nuclear reactions in the solar model,
will be of high scientific value as they will both increase our knowledge
of the sun and the nature of neutrinos.

Using \DtwoO\ as a target, SNO has the unique capability to measure
both the flux of electron neutrinos via the charged current
(CC) interaction as well as the flux of other neutrino flavours via the
neutral current (NC) interaction.  One can therefore observe the
reappearance of the oscillating $\nu_e$\ as a neutrino with a a different
flavour.  This is done with a modest detection efficiency in SNO until,
after one year of running with pure
\DtwoO, magnesium salt (MgCl$_2$) is
added to the \DtwoO\ in order to raise the NC detection efficiency to
83\%.  In the third year of the scientific plan, neutron detectors will
be inserted in the SNO detector to replace the magnesium salt, resulting
in a lower NC detection efficiency, but a potentially better separation
of the NC events from events resulting from $\nu_e$\ interactions.

Even before a precise measurement of the neutral current flux, the
oscillation models compatible with previous observations of the solar
flux can be distinguished after accumulating several thousand charged
current events.  How conclusive this observation will be will depend on
the result; and the statistical significance is unlikely to be
compelling.  It is therefore an important issue to determine how one
decides the duration of the pure \DtwoO\ data taking with a stable and
well-understood detector before moving on to the definitive neutral
current measurements.  During this period, SNO will also provide
information on the possible ``high-energy anomaly'' observed by the
SuperKamiokande collaboration in the form of an excess of events near the
endpoint of boron spectrum.  

Other science missions of SNO include measuring the properties
of atmospheric muons and the detection of galactic supernovae.  The
scientific importance of observing a supernova with a detector like SNO
far outweigh the low probability that such an event will occur during its
lifetime.  The participation in the SNEWS early warning network enhances
the science reach of this effort.  It will allow astronomers to make the
important early observations that were not possible with SN1987A. 

Finally, we note that of the currently operating detectors, SNO has the
lowest energy threshold and is sensitive to all species of both neutrinos
and antineutrinos.  This is a direct result of the very deep underground
location of SNO, which reduces backgrounds arising from cosmic ray muons,
and the very low radioactivity levels achieved by the collaboration in
the instrumentation and water.

In summary, with its potential for measuring the neutral as well as the
charged current interactions of neutrinos, SNO holds the key to solving
the solar neutrino problem.  It will possibly provide the first direct
observations of solar neutrino oscillations.  The detector has started
data taking with an adequate time window to deliver results before
competing detectors will be commissioned.

\section{Detector Commissioning Status}
%
\subsection{Operations - PKS/JW}

The SNO collaboration has made very good progress in commissioning the
detector over the last seven months since the water fill was complete. 
This was evidenced in all aspects of the experiment.  The team now is
focussed on understanding the detector and optimizing its performance.
Since the water fill was completed at the end of April 1999, all systems
of the detector have been commissioned and brought into routine operation.
Significantly, the last major changes to detector configuration were made
in the middle of October (the photomultiplier tube (PMT) high voltage was
increased by 100 V), and since then the collaboration has been focussed on
operating the detector with increasing efficiency, while at the same time
calibrating the detector and measuring background rates.

The electronics and data acquisition (DAQ) systems are operating smoothly,
with typical trigger rates in the neighbourhood of 15-20 Hz. 
The detector is operating with a typical trigger threshold of order 17 hit
tubes, corresponding to an energy threshold near 2.0 MeV.  The
``livetime'' of the detector -- in this case the fraction of time that the
detector was ready to detect supernovae events -- was reported to have
reached 94\%\ in the month of November, an impressive figure given the
complexity of the detector.  Livetime for solar neutrino collection was
significantly lower due to conflict between certain operations during
calibration and normal data taking.

The operations team appears to be well-managed and highly competent.  The
committee is confident that the necessary structure is in place to
operate the detector, although overall personnel resources are stretched
when one accounts for the large number of parallel tasks that must be
underway to support the calibration, operation and analysis activities.

\subsection{Calibration - PKS/JW}
%
The SNO detector has an arsenal of calibration sources designed to
measure the optical response of the detector, its energy resolution
and background rates. The optical calibration, performed using
a laser source and a diffuser ball suspended in the \DtwoO, appears to be
well understood, although this work is not yet complete.    An understanding of the optical transmission and detection of
photons is a fundamental issue, and must be established before a detailed
energy calibration can be completed. The committee was shown preliminary
results of the optical calibration, demonstrating that the agreement
between observed performance of the detector and the Monte Carlo (MC)
predictions was at the few percent level. 
The non-uniformities of the illumination of the source remain to be
completely resolved, though a reasonable plan exists to address this
issue.

Three calibration runs using a $^{16}$N source
that provides a 6.1~MeV $\gamma$\ have been performed, and this
calibration already provides an energy calibration at this energy
that has an uncertainty better than 6\%.  The ultimate goal is to have
an understanding of the energy calibration to an uncertainty of 1\%,
which requires periodic $^{16}$N runs and the deployment of additional
sources.  These calibration sources are:
\begin{itemize}
\item U and Th sources to measure the characteristics of the principle
background sources in the \DtwoO,
\item a ${\rm (p,t\gamma)}$\ source that provides a 20 MeV
$\gamma$\ calibration point,
\item a $^8$Li source to provide a $\beta$\ source with a continuous
energy to measure the efficiency of the ``data cleaning'' operations and
test the understanding of the detector's energy response, and
\item a number of lower-energy sources for background studies and
low-energy calibration points.
\end{itemize}
The collaboration has as its highest priority the analysis of the
existing calibration data and the deployment of the U, Th, ${\rm
(p,t\gamma)}$, and $^8$Li sources in order to meet its initial physics
milestones.  The reviewers agree with this strategy.

The collaboration noted that personnel resources may limit its ability to
implement these additional calibration sources on a schedule consistent
with the first physics milestone of May 2000.  The committee is not
convinced that the schedule is credible either, given the limited
personnel involved in the calibration effort.  The reviewers recommend
that the collaboration make every effort to identify additional
scientific personnel in order to ensure that these additional calibration
sources are deployed and the calibration data analyzed early enough to
allow SNO to meet its May 2000 physics milestone.

\subsection{D$_2$O, H$_2$O and Radioactive Backgrounds}
%
The  key to  the  SNO detector  is  the 1000  tonnes  of 
\DtwoO\ suspended  in a  spherical acrylic vessel  at the  centre of
7000 tonnes of light water ($H_{2}O$) shielding.  The light and heavy
water both  must be maintained  ultrapure for optical clarity  and low
background radiation.   The radioactivity in the water  is required to
be less  than one uranium disintegration  per day per  tonne of water.
The heavy water is valued at  300M\$ and therefore has to be accounted
for very carefully.  Although the heavy water is insured against a
catastrophic loss or  dilution with  light water, the cost  of
restoring heavy water that has been  diluted (downgraded) or lost through
normal operation is  considered part  of the operating  and
decommissionining costs.

The structural  integrity of  the acrylic vessel  is essential  to the
safe operation  of the  experiment.  Analysis of  the stresses  on the
acrylic require  the level of the  heavy water be  maintained within a
$0.5$~cm tolerance.  
The heavy  water itself is on loan  from AECL to the end of 2000. 
Negotiations  are underway to extend the loan, first to the end of 2001
and then to the end of 2003. The first  date is  well in hand and the
collaboration  is optimistic about achieving the second.

The  SNO water handling  team has  done a  highly professional  job of
designing,  building, commissioning and  operating the  water systems.
Moreover, they  have met a number of  significant challenges including
some unsuspected experimental conditions that became apparent once the
water was in place.  Some  important milestones over the last year are
noted here:
\begin{itemize}
\item February, 1999 -- Light  water regassed.  
\item May 1, 1999 -- Detector full.  
\item June, 1999 -- Radioactive assays start.  
\item July, 1999  -- Atmospheric pressure  of the deck changed  to exclude
 radon.   The cover  gas was  removed  from the  light water.   
\item August, 1999 -- A flow of  nitrogen gas is introduced to the neck
of the  acrylic vessel.   In November  the  gas is  humidified to  stop
static   electric  discharges.    
\item  September,   1999   --  The recirculation of  the $D_{2}O$ reaches 
the design flow rate  of 150 lpm.  Radon gas  levels decline.  
\item November, 1999  -- The radon levels  are   close  to  the  design 
criteria.    The first full $^{16}$N\ calibration is made.
\end{itemize}

The  water  operations  require   a  specially  trained  team  of  six
operators, four assistants and  three others in charge of maintenance,
cleaning  and other  functions.  The  team works  six  twelve-hour day
shifts  and  three twelve-hour  night  shifts  per  week.  The water
system may only be run when there are at  least two operators underground
at  the experiment.  The ongoing  operations include  running the 
circulation systems  for the heavy  and light water  and making 
radioactive assays.   Recently the water team  has moved one technician 
to the surface to  help with the assay  chemistry and funding for a
replacement for  the underground  position has been requested.   The 
committee supports  this  improvement  to the  water operation team.

The radiation  levels in the  water have improved and  are approaching
design.   Radon  levels are  an  important  indicator  of the  uranium
content of  the water, and weekly assays are scheduled.  Radon levels in
the \DtwoO\  have dropped to approximately the design criteria following
the stable  application of a flowing nitrogen cover gas for  the
\DtwoO.  The  price that  has to be  paid is a  loss of 200~ml of 
\DtwoO\ per  day.  The  radon in the  light water is nearing  design 
specification, with the largest source of radon appearing to  be from air
entering from the mine.  The  water  team  is working  on  sealing leaks
into the  light  water cover-gas volume. 

Assays for radium contamination in the \DtwoO\ are made to  estimate the
amount of uranium ($^{226}$Ra) and thorium ($^{224}$Ra) using MnO$_x$ and
seeded ultrafiltration techniques.   The uranium  assays  are at 
$10^{-15}$ gram U per gram water, well  below the required  levels.  The
thorium  assays have only  yielded upper limits  so far  that are  near
the  required  levels.  A direct observation  confirming the thorium 
concentration is required, and the collaboration is working on a high 
flow system  with eight parallel  columns of
MnO$_x$\ to solve this problem.  A system to detect
lead is also being developed (this is a .

The  water team is  also developing  the plant  that will  produce the
MgCl$_2$ brine  and remove  it from the \DtwoO.  This  operation is
critical for  the neutral  current measurement of  phase 2 of  the SNO
experiment.  The system will be  reviewed in the next couple of weeks.
The schedule  calls for  the brine to  be produced and  underground by
September 2000.

The total inventory of heavy  water received by SNO from Ontario Hydro
is 1,106,484  kg.  The  isotopic purity of  the bulk water  is checked
regularly and  has not changed.   Approximately 170 kg of  heavy water
has been  lost, mostly by  absorption in the acrylic  vessel.  Further
losses from evaporation  are expected to be 73 kg  per year.  The cost
of replacement  is approximately \$300  per kg.  Another 2025  kg have
been isotopically downgraded  as part of the initial  setup and due to
ongoing assays.   There is a further  30 kg that  is isotopically pure
but contaminated.  This water can be cleaned on site.

The downgraded water can be returned to Ontario Hydro for upgrading at
a cost of  \$8 per kg, so that the cost of upgrading the present
inventory  will be about
\$20~000.   The  SNO  collaboration  would  like  to 
start returning degraded  water to  reduce their stored  inventory. 
Ontario Hydro has requested a delay while it develops an appropriate
facility. Over  the longer  term  upgrading  costs are  expected  to be 
roughly
\$10~000 per year.

\section{Physics Analysis - PS/RK}
%
The SNO collaboration has over the last year put together a comprehensive
analysis plan, consisting of a series of ``supporting analyses'' and
a set of ``physics analyses.''  Working groups have been established for
each of the supporting analyses, although the personnel effort in many of
these groups is limited to only one individual (who in many cases has
multiple responsibilities).  Convenors have been identified for
organizing each working group, and a gant chart detailing the analysis
effort over the next three years has been developed.  Each  group
has clear goals and is working toward a common schedule and set of
milestones.

The organization of this analysis effort is an impressive first step
toward getting science out of SNO, and the reviewers applaud the
collaboration for the commitment to this structured process.  The
reviewers endorse the collaborations commitment to use the SNOMAN
framework as the basis for all ``final, publishable analyses.''  The
collaboration was able to report significant progress on all major
analysis fronts: software and databases, detector support, calibrations,
data flow, data cleaning and event characterization.  They have set as
important milestones the completion of the optical calibration by April
2000, the energy calibrations by July 2000 and a preliminary measurement
of the charged-current and elastic scattering (CC/ES) flux by February
2001.

However, much remains to be done, and personnel resources appear to
be a limiting factor in analysis progress.  There are approximately 10
full-time personnel working on solar neutrino analyses, an additional 6
physicists working partime on solar neutrinos, 4 physicists involved in
analysis of through-going muons, and 2 physicists working full-time on
the supernova watch.  Of these analysis efforts, the reviewers were
satisfied that sufficient resources were allocated to the latter two
topics.  However, the reviewers were very concerned that the analysis
effort on solar $\nu$'s was too dispersed and not sufficiently focussed. 
The collaboration reported that four independent groups were involved in
solar neutrino analyses.  Although it is important to have several
independent analyses on this topic, given it is where SNO is expected to
have the greatest scientific impact, the reviewers believe that four such
analyses are simply too many given the limited physicist
resources.  The reviewers recommend that the solar neutrino physics
analysis efforts be more focussed with a smaller number of independent
efforts.

\section{Management Issues - MV}
%
The SNO collaboration has taken significant steps over the last year
to improve its management structure.  The Scientific Management Committee
and the Senior Executive Committee were replaced by a Scientific Board (SB)
that meets at least monthly.  The SB includes one representative from
each SNO institute, the national spokepersons, the scientific officers
(director, two associate directors, analysis coordinator), and key group
leaders.  Two members are elected at large by the collaboration, with
the intent that they represent the junior members of the collaboration.
The scientific board is responsible for setting policy on topics such
as the length of data runs in each configuration of SNO, run plans within
each configuration, and publication and conference talks.  The board's
decision must be ratified by the collaboration.  This management scheme
seems to be working well.

The collaboration has also reorganized the supervision of the operation
of the water systems and the detector.  David Sinclair was appointed
as Associate Director - Science with overall responsibility for running
the experiment.  Tony Noble replaced Sinclair as Associate Director of
underground operations with main responsibility for the water systems.
Richard Van de Water is the head of the detector working group and is
responsible for the day-to-day operation of the detector systems.
Finally, Josh Klein is continuing as analysis coordinator.  This team
is effective and the committee feels that SNO operations run smoothly.

Last year's GSC site review committee expressed concern over the long
term staffing of key management positions related to the fact that
several individuals would have to return to teaching duties, or to 
retirements.  The SNO collaboration has responded to this issue by 
designating replacements and/or deputies for these key individuals,
and the situation seems to be in hand.

\section{Schedule and Longer Range Science Plan - KP/EB}
%
A.B. McDonald presented the SNO Long Range Plan (as of December 1999) to
the combined SNO-ARC Science Committee and the NSERC Review
Committee on the 8th December.  In essence, the plan proposes taking data
over the next three to four years to attack the solar neutrino problem in
four stages:
\begin{enumerate}
\item running in pure \DtwoO,
\item adding MgCl$_2$\ to the \DtwoO,
\item using the $^3$He Neutral Current Detectors (NCD's), and
\item running in pure H$_2$O.
\end{enumerate}

This is consistent with the main goal of SNO, which is to determine
independently the total flux of ``active'' neutrinos from the neutral
current (NC) interactions in heavy water and to compare this with the flux
determined only from the charged current (CC) interactions. The charged and
neutral current measurements are unique to SNO. When complete, this should
allow the different possible solutions to the ``solar neutrino problem''
(large
and small angle MSW effect, ``just-so'' vacuum oscillations, sterile
neutrinos) to be resolved.

The scientific goals for the four stages outlined above are clear, and are
detailed below.
\subsection{Running in Pure D$_2$O}
The scientific objectives for running with pure heavy water are:
\begin{itemize}
\item to measure the integral ne flux with the CC interaction with
$E_n>7.5$~MeV,
\item to measure the energy spectrum with CC interaction with
$E_n>7.5$~MeV,
\item to measure the integral $\nu_e$\ flux with the Elastic Scattering
(ES) interaction with $E_n>7.5$~MeV,
\item to make an initial measurement of the ES/CC ratio, and
\item to make an initial measurement of the NC/CC ratio.
\end{itemize}
This last measurement will require a proper understanding of the
radioactive
backgrounds.

This is a sensible initial programme, which will allow experience to be
gained with running the detector over an extended period in stable
conditions, and will also test the calibration, data reduction and data
analysis techniques. The results from the ES interactions could be compared
to the SuperKamiokande data.

A sufficiently precise measurement of the spectral shape could, in
principle, yield valuable information on the origins of the neutrino
oscillations, but this probably requires a longer run for this to be
statistically significant than is justified, given the importance of the NC
measurements. There is a risk that a measurement of the ES or NC rate,
combined with the CC rate and the SuperKamiokande data, will allow almost
anyone to do 'quick and dirty' analysis to 'resolve' the solar neutrino
problem. The collaboration needs to have a clear strategy for deciding
what data can be shown publicly.

\subsection{Adding MgCl$_2$}
%
By adding salt (MgCl$_2$) to the \DtwoO, the sensitivity to neutral
current events
is significantly enhanced. Techniques have now been developed which allows
the NC/CC ratio to be deduced statistically from the data, making this a
robust technique. The operation is relatively quick - it should take about
a
week to introduce the salt though a brine solution - and reversible -
removing the salt by reverse osmosis will take about one month. This should
yield the first statistically significant measurement of the NC/CC ratio.

Given that this procedure is relatively quick, and could be repeated should
problems or inconsistencies arise, it makes sense to perform this test
early.

Would we like to see a technical evaluation of the impact of MgCl2 on the
integrity of the acrylic vessel?

\subsection{Using the $^3$He Neutral Current Detectors}
%
The NCDs enhance the sensitivity for NC
detection by using 3He counters. This allows NC events to be recognised on
an event by event basis, and may help reduce the systematic errors on the
measurement of the energy spectrum.

The deployment of the NCDs is a major interruption to the schedule, and
is estimated to take about 3 months, during which time the detector is
open. [The SuperNova detection system will also be off during this time.]
The deployment is not easily reversible, although it will be an advantage
to identify NC events individually.

\subsection{Running in pure H$_2$O}
%
The main objectives are to confirm the radioactivity backgrounds and the ES
measurements. It is clearly prudent to plan this at some stage, but for
practical reasons this should be done last.
%
\subsection{Discussion and Recommendations}
%
The proposed long-range plan defines a coherent programme for achieving the
scientific goals of the experiment. However, the Committee was not given
sufficient detail to be able to judge whether this ambitious programme was
realistic in the timeframe suggested.  The committees make the following
comments and recommendations: 
\begin{enumerate}
\item The Committee endorses the general strategy for the NC measurements.
In particular, the Committee believes that it is essential that the 
MgCl$_2$\ run be completed before deployment of the NCD's.
%
\item The Committee is concerned that there is no set of criteria which
determines the time at which the change over from pure \DtwoO\ to
\DtwoO+MgCl$_2$\ takes place.
%
\item The Committee would like to see a set of milestones against which
progress for at least the first two stages of the long- term plan can be
measured and monitored. The Committee recognises that this is an ambitious
programme, and is concerned that without a clear schedule against which to
operate, the scientific goals might be compromised.
%
\item The Committee believes that it will take at least until 2004 to
complete this programme of work, and that it is therefore important to
negotiate by June 2000 an extension for the use of the \DtwoO\ until at
least 2004.
\end{enumerate}


\section{Photomultiplers, Bases and the HV Connectors}

Last winter there were very serious problems with ``wet-end breakdown''
in the HV connectors leading into the photomultipler tube (PMT) bases.
Since the regassing of the light water that surrounds the PMTs with
nitrogen in March 1999, the breakdown problem in the connectors has been
dramatically reduced. The detector has operated stably with minimal
problems from high voltage breakdown or tube loss since that time.
The PMT death rate, from all causes, based on about 6 months of
operation, is presently 0.4\% per year or about 1 per week, well in
line with other large water detectors. Wet-end breakdowns still occur
so there is no evidence that the HV problems are completely solved but
there is no indication at this time that a connector replacement
program will be needed.

The SNO collaboration has followed the recommendations of the External
Advisory Committee on the High Voltage Connector, which reported to
SNO-ARC in April, 1999.  Several on-line and near-line monitoring tools
have been implemented to track high voltage effects such as the
presence of ``sharkfin'' pulses and blown terminator resistors in the
PMT base to give an early warning of the onset of problems.

Sharkfins are large charge pulses with no light present, which are
assumed to be due to micro-discharges in the connector. They appear as
events in the ESUM trigger and can be monitored with the random
PULSE\_GT trigger. As they are characterized by a large ($>100$~mV) pulse
in one channel with pick-up in several nearby channels on the same HV
distribution card, they can be easily identified for monitoring and
for removal from the neutrino trigger data during the data cleaning
process. The wet-end breakdowns are known to blow the terminating
resistor in the PMT base after tens of discharges and this can be
monitored by reflection tests or by checking for gain increases in a
channel, since the loss of the 75~Ohm resistor causes the gain to
double. If the sparking persists the series resistor can open, causing
the tube to become inoperable.  Another problem leading to tube loss
is a water leak into the connector or PMT base which causes the high
voltage to short out.

The most serious problem in terms of the neutrino background are
``flashers,'' which are light emitting breakdowns inside the PMT. The
light is picked up in several surrounding tubes and in tubes on the
opposite side of the detector. These are not HV connector related and
a significant fraction of the tubes exhibit flasher behaviour. Seismic
activity increases the rate of flasher events. A sufficiently large
number of tubes are involved to show up as a neutrino trigger, which
currently has a threshold set to 18 hit tubes. The flasher signature
has now been well defined so that these events can be removed during
the data cleaning, although the efficiency of doing this has not been
determined as yet.

In October 1999, the voltages on all PMTs were increased by 100~V to
improve the signal/noise and provide the design sensitivity threshold of
0.25 photoelectrons. During this increase the HV phenomena were closely
monitored.  Both the sharkfin and flasher rates increased and then
settled to acceptable rates; sharkfins from 1.5~Hz to 2.5~Hz and
flashers from 30 per hour to 50 per hour. The tube loss rate since
that time has not noticeably increased. There are presently 160 PMTs
not functioning in the detector, with most of these due to failures
before the regassing was carried out in March.

Two other recommendations of the External Advisory Committee on the HV
connectors were for the SNO collaboration to develop and test a replacement
high voltage connector and to produce an implementation plan showing the cost
and time impact if a repair were necessary. A new connector design has been
produced but only variations of this connector have been tested to date. A
draft report on the SNO Detector Connector Repair was submitted to the
SNO collaboration and to the SNO-ARC Science committee at this meeting.
The main conclusions/recommendations of the draft report, which still
needs to be reviewed by the collaboration, are as follows:
\begin{itemize}
%
\item If a connector repair is required, a new wet-end male
connector/full cable assembly replacement represents the best
understood methodology at this time. (We note that this is solution
1. as recommended by the External Advisory Committee.)
%
\item A dry repair with full cable assembly replacement will cost 5.18
million 1999 Canadian dollars, and will take 12.5 months of detector
non-operation.
%
\end{itemize}

The committee has the following recommendations for the collaboration:
\begin{itemize}
%
\item Continue the close monitoring of the detector HV performance.
%
\item Complete the development and fabrication of the production
prototype of the replacement connector and test 10-20 of these, first
in an initial long-term test at TRIUMF to be completed in 6 months and
then in the SNO detector using the Berkeley underwater test sleds.
%
\item The External Advisory Committee on the High Voltage Connector
should continue to receive bi-monthly reports on the HV performance.
%
\end{itemize}

\section{Future Science Opportunities - FH/KP/MV}

\section{Summary of Recommendations - PKS}
The recommendations outlined in the report are summarized here:
\begin{enumerate}
%
\item The collaboration review the personnel requirements for the
deployment of the highest priority calibration sources (U, Th, 
${\rm (p,t\gamma)}$, and $^8$Li) and the associated analysis efforts.
%
\item The collaboration focus the solar nuetrino analysis efforts to make
use of limited personnel resources in as effective a way as possible. 
The number of independent analyses should be reviewed and perhaps reduced.
%
\item The Committee endorses the general strategy for the NC measurements.
In particular, the Committee believes that it is essential that the 
MgCl$_2$\ run be completed before deployment of the NCD's.
%
\item The Committee is concerned that there is no set of criteria which
determines the time at which the change over from pure \DtwoO\ to
\DtwoO+MgCl$_2$\ takes place.
%
\item The Committee would like to see a set of milestones against which
progress for at least the first two stages of the long- term plan can be
measured and monitored. The Committee recognises that this is an ambitious
programme, and is concerned that without a clear schedule against which to
operate, the scientific goals might be compromised.
%
\item The Committee believes that it will take at least until 2004 to
complete this programme of work, and that it is therefore important to
negotiate by June 2000 an extension for the use of the \DtwoO\ until at
least 2004.
\item The collaboration should continue the close monitoring of the
detector HV performance.
%
\item The collaboration complete the development and fabrication of the
production prototype of the replacement connector and test 10-20 of
these, first in an initial long-term test at TRIUMF to be completed in 6
months and then in the SNO detector using the Berkeley underwater test
sleds.
%
\item The External Advisory Committee on the High Voltage Connector
should continue to receive bi-monthly reports on the HV performance.
%
\end{enumerate}

\section*{Appendix A:  Funding Recommendations}
\section*{Appendix B:  Membership of SNO-ARC Science Subcommittee}
%
\begin{itemize}
	\item Prof. Pekka Sinervo, Department of Physics, University of Toronto
(chair)
	\item Dr. Ewart Blackmore, TRIUMF
	\item Prof. Francis Halzen, Department of Physics, University of
Wisconsin 
	\item Prof. Ed Kearns, Department of Physics, Boston University
	\item Prof. John Martin, Department of Physics, University of
Toronto
	\item Prof. Ken Peach, Particle Physics Department, Rutherford
Appleton Laboratory
%
\end{itemize}

\section*{Appendix C:  Membership of the NSERC SNO Review Committee}

\begin{itemize}

	\item Dr. Michel Vetterli, TRIUMF (chair)
	\item Prof. Enrico Bellotti, Milano
	\item Prof. Patricia Kalyniak, Department of Physics, Carleton
University
	\item Prof. Richard Keeler, Department of Physics and Astronomy,
University of Victoria
	\item Prof. Jim Waddington, Department of Physics, McMaster University
	\item Ms. Kate Wilson, Team Leader for Subatomic Physics and Astronomy,
NSERC (observor)
\end{itemize}

\section*{Appendix D:  Agenda for Review}
\begin{verbatim}
Wednesday, Dec.8th: SNO Project Status
--------------------------------------

 9:00 Committees in camera (15)
       - organisation of the two committees

 9:15 Introduction  A.B. McDonald (15)
 
 9:30 Status of Experiment (35) D. Sinclair
       - overview of commissioning
       - status of outstanding problems from last year
       - what new problems have arisen?
       - prospects for physics results

10:05 Water (35) T. Noble
       - rate of loss of D2O
       - status of degradation
       - assays: time & number
       - contamination levels
       - status of MnO2 fabrication
       - status of MgCl2

10:40 COFFEE

10:55 Detector (30) R. Van de Water
       - PMT's (status of HV breakdown)
       - electronics & DAQ
       - monitoring

11:25 DAQ (15) A. Hamian
       - DAQ status
       - Future development

11:40 Analysis (45) J. Klein

       Organisation

       Technical:
       - status of software & databases
       - status of data reduction
       - online analysis

       Physics:
       - analysis chain & software
       - Monte Carlo studies
       - prospects for physics results

 12:25 LUNCH

 1:25 Calibration (30) A. Hallin
       - what has been done?
       - current development of new sources
       - future sources

 1:55 3He Detectors, U.S. Status H. Robertson (15)

 2:10 Discussion of morning session (20)


 2:30 Scientific Priorities & Strategy (45) A. McDonald
       - Time required for CC measurement
       - Competition
       - Neutral Current Measurement

 3:15 COFFEE

 3:30 Special Topics
       - Supernova Detection (15) C. Virtue
       - Muons, Atmospheric Neutrinos (15) C. Waltham

 4:00 Discussion of afternoon session (30)

 4:30 Committees in camera (60)

 5:30 Close-out meeting

 5:45 Adjourn

 7:00 Working Dinner

Thurday, Dec.9th
----------------

 9:00 Committees in camera (60)

10:00 COFFEE

The two committees will split at this point.

Schedule for GSC Committee
-------------

Operations Grant:
----------------

10:15 Site Operations Grant (60) McDonald, Sinclair, Hepburn,
Noble
       - Services funded by this grant
       - Staffing requirements
       - Budget
       - Organisation

Institutional Grants:
--------------------

11:15 Overview (20) A. McDonald
      - Group responsibilities
      - # of people to satisfy these responsibilities
      - Typical travel costs  

      This information should be given in tables we 
      can refer to in later presentations.  Questions 
      to be reserved for individual groups.

11:35 Queen's (20) A. Hallin

11:55 Carleton (20) D. Sinclair

12:15 LUNCH

 1:15 Guelph (20) J. Simpson

 1:35 Laurentian (20) D. Hallman

 1:55 UBC (20) C. Waltham

 2:15 General Discussion

 2:45 COFFEE

 3:00 GSC Committee in camera (60)

 4:00 Close-out meeting

 4:15 GSC Committee in camera (60+)

      Adjourn when required for travel



Thursday, Dec.9th

Schedule for SNO-ARC Sub-Committee
----------------
 9:00 Committees in camera (60)

10:00 COFFEE

The two committees will split at this point.

SNO-ARC Science Sub-Committee
-----------------------------
10:15 - 11:30  SNO-ARC Committee Meeting in camera

11:30 - 12:15 LUNCH

12:15 - 2:15 

  Calibration Details (A. Hallin) (20)

  HV Connectors (R. Helmer) (20)

  Run Plan (D. Sinclair) (30)

  Review of Plan for Neutral Current Detection (A. McDonald)(30) 

  Discussion of Possible Future Projects (A. McDonald) (20)

 2:15 General Discussion

 2:45 COFFEE

 3:00 SNO-ARC Committee Meeting in camera

 4:00 Close-out
\end{verbatim}

\end{document}

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