View on the TOT option for CBM-XYTER (toward specs)

E. Atkin, I.Ilyushchenko, A.Kluev, Yu.Volkov, MEPhI

A.Voronin, SINP MSU

13rd CBM Collaboration meeting, FEE section, 12.03.09 1

Aim

To present a status view of joint team (MEPhI/SINP MSU) on the CBM-XYTER FEE specs, relevant to TOT option

13rd CBM Collaboration meeting, FEE section, 12.03.09 2

Outline13rd CBM Collaboration meeting, FEE section, 12.03.09 3

• Starting points are:- CBM XYTER wiki - internet- some experience

• Signal shape & equivalent circuit => DR• TOT option for CBM-XYTER.• Jitter. Transient noise view.• Statement of other problems• Two versions of data-driven architecture• On the way tasks & conclusions

Current pulses in strip detectors13rd CBM Collaboration meeting, FEE section, 12.03.09 4

The duration of the electron and hole pulses is determined by the time required to traverse the detector as in a parallel-plate detector, but the

shapes are very different.H. Spieler . Front-End Electronics Systems for Particle Detection and Imaging – Signal Formation and Acquisition. 2008 IEEE Nuclear Science Symposium, p.8

Equivalent detector ckt. simplified(toward lumped model)

13rd CBM Collaboration meeting, FEE section, 12.03.09 5

… accurate matching with FEE via quality microcables (up to tens cm in length) needed

CBM strips are not micro, but long transmission lines

Signal dynamic range (SDD=2)13rd CBM Collaboration meeting, FEE section, 12.03.09 6

2 mips

1 mipThreshold

Transient noise

Effectivness improvement

How many ADC bits needed?13rd CBM Collaboration meeting, FEE section, 12.03.09 7

Threshold/base line noise

(4÷6):11:(0.7÷0.8)typ

From threshold (read LSB) to 2 mips (7.2 fC max) we should foresee 4-bit range

~ 70..80% part of cluster goes to strip

Part of noisy 1 mip/thresholdLSB

(?):1

We have quite rigit specs on the noise accurate filtering needed

Other factors related to signal shape and amplitude

(?):1

Very front-end tasks13rd CBM Collaboration meeting, FEE section, 12.03.09 8

• Statistics of detector signals

• Detector should be considered as a RF structure – long transmission line

• Strips-FEE cabling (up to tens cm length) also looks like a transmission line which makes a delay and change a pulse shape

• Radiation hard environment

What does the TOT option mean for CBM-XYTER?

13rd CBM Collaboration meeting, FEE section, 12.03.09 9

TOT methodically is a type of ADC and similar to Wilkinson (dual slope) one

Pulse measurement process in Wilkinson ADC:

How to put threshold? 13rd CBM Collaboration meeting, FEE section, 12.03.09 10

Three possible solutions for TOT 13rd CBM Collaboration meeting, FEE section, 12.03.09 11

Single slope TOT uses capacitor, charging by constant current source till the crossing of the signal falling edge

Direct TOT uses leading/falling edge comparator for time references

Schmidt trigger TOT (due to built-in hysteresis) uses lower threshold for the trailing edge triggering

Jitter (transient noise example)13rd CBM Collaboration meeting, FEE section, 12.03.09 12

Transient noise

Statement of other problems13rd CBM Collaboration meeting, FEE section, 12.03.09 13

• Balistic deficit • Double sided read-out• Leakage current (DC mode)

compensation versus noise • Type of shaping (CR-RCn and anti-

tail/anti-alias) both for amplitude measurements and timing

• Discriminator options (LE, CFD, ID) for timing

• Discriminator charge sensitivity• All versus long-term radiation • All versus power consumption

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Two versions of data-driven architecture

13rd CBM Collaboration meeting, FEE section, 12.03.09 14

Back-up architecture with cross-point switch is advantageous since it allows to perform a peak find function after derandomisation and therefore save power consumptionNow the derandomiser chip based on 12816 cross-point switch under development (A.Kluev). Pipeline ADC (Yu.Bocharov/A.Simakov) is expected to be one of the built-in block TOT study will trend us to incorporate front-end test structures. Prototyping late 2009.. beg. 2010

Mainstream solution is token-ring derandomisation

On the way tasks13rd CBM Collaboration meeting, FEE section, 12.03.09 15

- Direct agreements with Cadence and MG have signed for the next two years

- Europractice membership & DKs updated

- Expected are that 3 new PhD students for FEE development will be involved in the CBM FEE activity for 3 years starting from May 2009

- Other

Some references13rd CBM Collaboration meeting, FEE section, 12.03.09 16

1. S. Godowsky, M. Turala, et al. Pulse shapes of silicon strip detectors as a diagnostic tool. NIM A, 1993, Volume 326, Issue 1-2, pp. 239-242.

2. P. Allport. Silicon strip detector designs for the ATLAS experiment. NIM A, vol. 386, 1997 pp. 109–116.

3. R. Kollipara, A. Arodzero, J. Brau et al. Study of 18-cm long single-sided AC-coupled silicon microstrip detectors IEEE Trans. on NS, Vol. 42,  Issue 2,  April 1995 , pp.92 – 101.

4. H. Spieler . Front-End Electronics Systems for Particle Detection and Imaging . Signal Formation and Acquisition. IEEE Nuclear Science Symposium, Dresden, 2008, p.8.

5. F. Goulding, D. Landis, Ballistic deficit correction in semiconductor detector spectrometers, IEEE Trans. on NS, vol. 35, issue 1, 1988, pp. 119-124.

6. Dušan Kollár,  Pulse processing and Analyses, DNP, FMFI UK Bratislava, www.dnp.fmph.uniba.sk/~kollar/je_w/el3.htm#5b

Some conclusions13rd CBM Collaboration meeting, FEE section, 12.03.09 17

- TOT option should be considered as an ADC block

- For amplitude measurements 4-5 bit (6 bit?) resolution ADC needed at lowest power consumption

- Filtering is to be studied versus jitter and time walk taking into account other system problems

- Different ways for power consumption minimizing is to be studied both at the block and architecture (system) level

- Detector signal family (for both sides) is to be studied as well as multichannel equivalent circuits