AIDA Meeting - CCLRC RAL - 5 July 2006
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Present:	Tom Davinson (by telephone)			Edinburgh
		Rob Page					Liverpool
		John Simpson, Ian Lazarus			CCLRC DL
		Marcus French, Mark Prydderch, Stephen Thomas	CCLRC RAL

Summary of meeting
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Extended discussion of discriminator and timing issues
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Channel to channel variations in gain, offset etc. imply problems
obtaining uniform threshold across many channels

	programmable variations of offset/threshold
	design time required

High gain mode (20MeV FSR) 

	threshold 0-2MeV (0-10% FSR)
	jitter?
	comparator type? leading edge/crossover/dual threshold

Typical Si detector risetimes c. 100ns/mm
	should not specify time resolution beyond intrinsic detector limitations
	assumption: risetime will be dominated by CMOS preamplifier?

Physics requirements
	isomer lifetimes > 10ns
	isomeric Beta-decays => threshold as low as possible

Note:	There appears to be a conflict of requirements here.

	We require a low threshold for acquisition of low energy beta events
	(threshold should be <50keV, ideally 25keV). To me this implies 
	a bandpass filter with long shaping times to achieve rms noise <
	0.2x required threshold, i.e. slow trigger

	On the other hand, we also want good time resolution (or, at least,
	better than than the BUTIS 200MHz system clock) which implies short
	shaping times to maximise the slew rate through threshold and therefore
	minimise jitter. This probably implies a non-optimum signal:noise
	ratio and therefore a higher threshold.

	Have I missed something? Or does the proposed spec imply two 		
	discriminators, i.e. energy _and_ timing thresholds. By extension,
	all events would have energy information but some would be missing
	timing information.

Processing time
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Shaping time > 5x maximum risetime to minimise ballistic effects

	CR-RC shaping
	risetime 0.05xCR	~0.2%
		 0.10xCR	~0.5%
		 0.20xCR	~2.5%

Variable shaping time?

	prototype only
	CR-RC
	0.5-5us

16-bit ADC (use 14 bits), conversion time 3us

Zero-suppressing MUX

Effects of radiation damage
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Expect leakage current to increase by x10-x100

Typical leakage currents 	1-3nA/cm^2/100um
(no radiation damage)
				
	Max strip area 3 x 0.625mm x 80mm = 150mm^2

				15-45nA per strip

SLT Presentation of Initial Study of Overload Recovery Simulations
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SLT presented an initial study of the effect of overload and subsequent
recovery times. Should be regarded as a reconnaisance to understand which
factors are important to overload recovery.

Summary

		overload recovery can work
		depends critically on (unknown) input pulse shape
		other factors, e.g. cable length (15cm) affect response too


Meeting included discussion of possible tests during the forthcoming RISING
active stopper campaign at GSI. Objective to understand pulse shape of the
multi-GeV heavy-ion implants, crosstalk effects etc.

T.Davinson - August 2006