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\newcommand{\cc }{$^{12}$C}
\newcommand{\oo }{$^{16}$O}
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\begin{document}

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\noindent
\begin{picture}(0,0)
\put(0,2.5){\makebox(0,0)[l]{CH/Meet/92/06}}   %% Reference number of document
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\noindent
\begin{minipage}[t]{10cm}
\fbox{
\parbox[t]{5cm}{
{\large {\bf Minutes}}\\[2mm]
Charissa Group Meeting
}}\\[7mm]
\makebox[3.5cm][l]{Meeting held on:} 25 November 1992\\[2mm]            % Date
\makebox[3.5cm][l]{Meeting held at:} York \\[2mm]     % Place
\end{minipage}
\hfill \raisebox{-2.5cm}{
\psfig{figure=char-encap.ps,height=3cm}}\\[2mm]

\begin{center} \begin{tabular}{l@{~~}l} \hline
~\\								% Present
\makebox[2.5cm][l]{Present:} & \parbox[t]{12cm}{
BRF(Chair),WNC,NMC,RAC,GJG,SJAH,RAH,CDJ,JK,JSL,\\WDMR,RPW,DLW
}\\
~\\								% Apologies
\makebox[2.5cm][l]{Apologies:} & \parbox[t]{12cm}{
ACM,VP,GT
}\\
~\\								% Distribution
\makebox[2.5cm][l]{Distribution:} & \parbox[t]{12cm}{
Those present, plus  BB,ACM,VP,GT
}\\
~\\ \hline
\end{tabular}
~\\[0.5cm]
%\addtolength{\headheight}{2.5cm}
{\large {\bf Minutes}} \\[0.5cm]
 \end{center}


\begin{enumerate}
%\addtocounter{enumi}{-1}

\item	{\bf Minutes of Meeting of 7 October 1992:} Accepted as a true record.
	
\item	{\bf Matters Arising:}\\
	Drs Steve Hall and Roger Ward (both Birmingham) were welcomed to
	the collaboration.

	WDMR requested that a bare-bones agenda be circulated by e-mail,
	in addition to the  version available over the fileserver.
	This was agreed. \action{WNC}

\item	{\bf Update on NSC/SERC matters:} there was nothing urgent to report,
	so this item was skipped due to the long agenda.
 
\item	{\bf Progress on Silicon Detectors:}\\
	BRF reported on the results obtained by M. Leddy (Birmingham)
	for beam tests of two Q--Par 2D position sensitive detectors
	(see Ch/Tec/92/11 for preliminary results).

	The sheet resistances of 1 and 2 k$\Omega /\Box $ were too low for
	good position resolution, but a higher resistance would solve this.
	A new detector is likely to be available for testing, early in 1993.

	The discussion at the meeting noted that the surface barrier
	technology appeared to give large distortions that would require
	position corrections.

	CDJ reported regarding the NASA-style detector supplied by Micron.
	York are analysing data from a beam test, but the results so far are
	inconclusive.

	BRF reported that
	the  test detector offered by Intertechnique had not arrived.

	The Hamamatsu detector should be beam-tested in conjunction with
	one of the remaining NSF runs. Other detector tests will also need to
	be tied in with the experimental runs, due to the prioritization
	by the NSC subcommittee of remaining NSF proposals. This can be
	achieved most effectively if Birmingham coordinate the tests.
	SJAH agrred to take responsibility. \action{SJAH}
	

\item	{\bf Progress on Scintillator Detectors:}\\
	NMC reported that the prototype ordered from Bicron (via Southern
	Scientific) had just arrived. The drawings supplied to Bicron had not
	been properly followed, and as a result the CsI crystal was machined to
	the wrong shape and was not usable. The detector had been returned
	with the error pointed out, and a response was awaited.

	NMC stated that the order placed with John Caunt was being processed
	on schedule. Components had begun arriving for assembly by the
	supplier and it was hoped to produce 25 detectors by the end of the
	year, and a further 25  early in January 1993.

\item	{\bf Progress on Chamber and Detector Assemblies:}\\
	{\it New chamber:}
	JSL reported on a preliminary design for the new forward-angle
	target chamber for five modules (each $3 \times 3$ detectors),
	as shown in  Daresbury  drawing A0--32/8039 (`Proposed
	Chamber (5 module)', S.J. Metcalf, 4/9/92). The drawing and a list of
	discussion points were circulated at the meeting (Ch/Tech/92/12).
	The construction timescale is for summer 1994 completion. 

	The proposed chamber incorporates  features as requested apart
	from a cold shroud, which could be incorporated by
	compromising the gamma-ray access.

	The meeting endorsed the choice of a Eurogam-type target controller,
	so long as manual over-ride was included. \action{MEGHA}

	A list of relevant equipment for a `minor equipment' bid is to be
	forwarded to BRF before 25 December. \action{JSL,JK}\\[1mm]

	{\it New detector modules:}
	A mock-up  of the prototype CsI module and mount had been built by York
	and was shown at the meeting.

	RAC and SJM (Daresbury) , liaising with Barney Brooks (Oxford),
	had advanced the design of the rear flange for the nine-detector
	modules, to incorporate all preamplifier mountings and electrical
	feedthroughs. This was included in Daresbury Drawing
	A0--NSE/SC/138, Issue A, `9 telescope module', S.J. Metcalf, 20/11/92).
	(To be renumbered as 32/8041 when completed.)

	Features of the design are:
	\begin{enumerate}
	\item	one multi-pin feedthrough supplies all scintillator
		voltages, which are then chained around 
		inside the module,
	\item	there are
		separate coaxial feedthroughs for each scintillator signal,
	\item	one 16-pin ($2 \times 8$) feedthrough deals with each 
		silicon/gas detector (this includes lines used as
		shielding). 	Hence, there is an array of 
		$3 \times 3$ feedthroughs on the back plate,
	\item	For the vertical groups of 3 detectors, plug-on modules 
		contain the Oxford preamps on motherboards and their metal
		cans shield the boards. Signals are 
		connected by twisted pair to BNC's on the backs of the cans.
		\end{enumerate}

	The proposed design was discussed and the following points raised:
	\begin{enumerate}
	\item	motherboard spares: to ascertain the number to be kept on hand,
		the preamp failure rate should be measured when the necessary
		number are available for testing, \action{WDMR,BB}
	\item	vacuum sealing screws: the size and number of 
		retaining screws were of concern to some. 
		These should be reassessed when a prototype is built,
	\item	replacement/mounting of silicon: contrary to the understanding
		of the design group, the silicons are in fact the `weakest
		link' in the design, because they will die due to beam exposure
		over one experiment, and will require replacement. The ease
		of replacement of silicon detectors
		without damaging them should be
		borne in mind, \action{MEGHA}
	\item	A means of testing individual modules on the bench-top should
		be considered as there is a need to check
		silicon operation quickly and efficiently 
		(e.g. using a blanking window, etc.). \action{MEGHA}
	\end{enumerate}

\item	{\bf Progress on Gas Supply:}\\
	The Megha committee is progressing satisfactorily
	with this. RAC discussed
	a schematic of the proposed new gas handling
	(Daresbury Drawing A3--32/8042, Issue A, `Schematic Megha Gas',
	9/11/92, S.J. Metcalf).

	Air freight of the gas rig may not be required (cf. advice from
	D.C. Weisser
	regarding sea freight), so space restrictions can be relaxed a little, 
	whilst still keeping the rig as small as is convenient. \action{MEGHA}

\item	{\bf Progress  on Electronics and Data Acquisition:}\\
	{\it Voltage-to-time conversion:} RAH circulated a document
	(Ch/Tech/92/13) describing the latest developments. This involved
	tests of a prototype analog-to-time convertor (ATC) circuit connected
	to a Silena sample-and-hold chip. Results suggest that the linearity
	is good to $<1:4000$, which is within the performance of the Silena
	ADC itself. Hence, 4K conversion range is indicated. An ATC conversion
	range of 8$\mu $s was sufficient to achieve this accuracy, giving
	a total conversion time of $\sim 12\mu $s, compared to 32$\mu $s at
	present.

	{\it Amplifiers:} A new half-width module using the existing 
	amplifier circuit 
	was displayed at the meeting. A prototype setup is being constructed,
	for testing on the bench-top with three germanium detectors.
	The new slim-line construction can be extended to incorporate the ATC
	vertically below the amplifier in a unit to fit a double-height
	Euro frame.

	It was noted that gains of up to 1K would be required to accommodate
	the gas detectors. Time constant values were still to be finalised.

	WDMR described how a previous problem with pole-zeroing of position
	signals could be removed when taking signals from both ends of
	the  resistive strips, and agreed to include this in  documentation
	(cf. Item 11).

	{\it Preamplifiers:} The two modified units, using surface mounted
	preamps, had worked well in the recent experiment (\mg +\mg ).
	Two high-gain versions for gas detectors will be produced for the
	next experiment. \action{WDMR}

	{\it Centralized Store of Equipment:} Transport to Oxford
	of the electronics recently purchased for data acquisition was in
	hand, and not causing any delays. 

	Small labels with the Charissa logo
	were required, to fit on the front of modules. \action{DLW}


\item	{\bf Developments on Hybrid Detectors:}\\
	RAC reported that the required alterations to the present hybrid
	detectors had been completed: new O--rings are installed, extra
	windows made, and the 6$\mu $m windows can be replaced by 1.5$\mu $m
	for low pressures as used currently. Right-angles gas connectors are in
	hand for the high-resolution run.

	If future detectors have thicker PCB's, they can be fitted
	using spacers.

	The noise problem in Detector 3 is still to be traced. \action{RAC}

	RAC is to be advised of window thicknesses for the next 
	run. \action{NMC}


\item	{\bf Developments on Event Manager and GEC Emulator:}\\
	BRF reported on the latest developments:

	{\it GEC emulation:} Two emulators had been assembled: one for use in
	an experiment and one 
	as a spare and for Oxford tests. Testing of an emulator connected
	to an event manager at DL was underway, with the aim of using an
	emulator in one of the remaining runs at the NSF.

	The emulator system is planned as an intermediate solution to the
	question of data acquisition, and following the shift to VME we
	anticipate an evolution to a new system.
 
	{\it ANU Data Acquisition Station:} Two systems had been ordered,
	each comprising a workstation, an exabyte drive and 2 Gbyte disk.
	This provides a backup that would also allow off-line analysis of
	existing data to proceed efficiently.

	With one or two additional small items, the reliability of the
	system could be further improved, and WDMR and RAH agreed to consult
	and inform BRF of these requirements. \action{WDMR,RAH}

	{\it Longer Term Software Requirements:} a data acquisition program
	would be required to replace the GEC emulator system in, say, two
	years, and alternatives should be investigated during the coming
	year. \action{SJAH}


\item	{\bf Documentation of Experimental Setup:}\\
	It is now apparent that proper documentation is needed for all aspects
	of the experimental set-up and procedure, particularly for when
	experiments are overseas.

	A note from BRF, circulated with the Agenda (Ch/Agen/92/06) was
	discussed.
	It was agreed to produce a draft version of the documentation in time
	for the next meeting, on January 27, and the following responsibilities
	were assigned:
	\begin{itemize}
	\item \makebox[7cm][l]{Chamber \& Gas:}		York
	\item \makebox[7cm][l]{Electronics:}		Oxford
	\item \makebox[7cm][l]{Data Acquisition:}	Birmingham
	\item \makebox[7cm][l]{Running:}		Surrey
	\item \makebox[7cm][l]{GEC Idiot's Guide:}	Birmingham
	\end{itemize}

\item	{\bf Completion of Programme at NSF:}\\
	The prioritization of the remaining approved experiments was noted.

	A note from BRF, circulated with the Agenda (Ch/Agen/92/06) was
	discussed.
	The implications were discussed with reference to students'
	requirements, and particularly second year students. It was agreed
	that York and Birmingham representatives would discuss this
	further. \action{DLW,BRF}

\item	{\bf Responsibilities for ANU preparation:}\\
	WDMR suggested that best results would be obtained if the personnel
	primarily responsible for the planned experiments were those that
	spent the longest time at the ANU in advance of the runs.

	Shipping:
	it was noted that a crate due for despatch to the ANU in June has
	some space available that could be utilised for beam-line components.

	A note from BRF, circulated with the Agenda (Ch/Agen/92/06) was
	discussed, and the following responsibilities were agreed:
	\begin{enumerate}
	\item {\it Detector mounts and Collimation:}\\
		Hybrid Detector Mounts are a high priority. \action{DLW,CDJ}
	\item {\it Chamber Feedthroughs:} \\
	number and type urgently to be decided, as these
	affect cabling requirements. Details needed for an order
	to be obtained on the next visit to the ANU 
	(Feb 93). Coordination to be  by York. \action{DLW}
	\item {\it Cable Runs:} \\new cable
	runs from the chamber to the control room
	to be organised by Surrey. \action{WNC,GJG}
	\item {\it Gas Flow System:} \\RAC agreed to check that the gas system
	will not be a problem. \action{RAC}
	\item {\it Electronics and DA system:} \\shipping and installation to be
		organised and undertaken by Birmingham, in consultation with
		RAH/VP where necessary. \action{BRF,NMC}
	\end{enumerate}


	Specific Queries: these can be directed to Paddy Regan, the local
	contact point at the ANU, on PDR103@nuc.anu.edu.au using e-mail.

\item	{\bf Student Training:}\\
	DLW noted the need for a plan to ensure that all students in the 
	collaboration are adequately provided with training in experimental
	technique. Further discussion was deferred due to time limitations,
	and DLW agreed to produce a discussion document for circulation to
	group members. \action{DLW}

\item	{\bf Future of the DL Detector Laboratory:}\\
	It was agreed to send a note to DL, stating that we  assume
	the detector laboratory is to remain in operation,  that all the
	equipment will remain in it, and that if the situation is different from
	this we will be informed. \action{BRF}

\item	{\bf Disposal of NSF radioactive sources:}\\
	There were no collaboration-specific needs, and hence bids for
	these items were a matter for individual groups.

\item	{\bf Disposal of NSF ``minor'' equipment:}\\
	Each group agreed to provide BRF with a list of items required
	for their contribution to Charissa activities by 9 December, and
	if possible to indicate what other items might be included in their
	total bids. \action{ALL}

\item	{\bf Any Other Business:} \\
	It was noted that the meeting to discuss ``European Collaboration
	on Heavy Ion Mechanism Reaction Studies'', in the context of the EC
	Human Capital and Mobility Program, would be held
	in Legnaro Laboratory, Padova, Italy on 16--18 December
	(cf. Ch/Doc/92/09, info from Multics Group). DLW will attend to
	represent Charissa. \action{DLW}

\item	{\bf Date of Next Meeting:} \begin{minipage}[t]{9cm}
	11.00 am, {\em Wednesday} 27 January 1993, \\in Birmingham.
	\end{minipage}

\end{enumerate}

\mbox{}\\
W.N. Catford, Secretary.\\
December 7, 1992\\[1mm]
(released \today )

\end{document}