TC detector

Flavio Gatti - Univ. and INFN of Genoaon behalf of the TC Group

PSI- Review Meeting, 17 Feb. 2010

Status in RUN 2009

Longitudinal detector (Bars+PMTs): it has operated as in RUN 2008 without HW changes.

Transversal detector (Fiber+APD): the readout electronics has been modified for achieving faster output pulses.

Diff. out (-)

Diff. out (+)

Total output80 ns

~20 ns risetime

Longitudinal Detector Performance Small worsening of timing resolution (see next talk by Cecilia) Check under way:

Baseline noise/EMI at the Disc input worse than in 2008 Optical coupling (silicone grease, air gap, absorption) PMT Gain: Re-measure PMT gain of 4 selected bars (8-PMT)

20082009 Intrinsic resolution

(jitter of e+ timeof flight not included)

Most probable origin: higher baseline noise @ discriminators (DTD) input Baseline oscillates (50Hz) with amplitude of 15 mV While a moderate threshold decrease improves timing res., a further decrease

gives worse results (10mV). But 10 mV threshold was the value used in the beam test! High level of signal cleanliness is needed for best performances. Some further

improvement must be achieved, taking care (monitoring) the baseline noise

Baseline @ Disc input

Baseline sampled at high freq.

New APD FE electronics

New electronics based on voltage amplification of APD current signal on noise matched resistor R3

The boost capacitor reduce the quenching effect of HV line resistors enhancing signal in proximity of breakdown point

RMS noise value of 25mV in the 20MHz BW achieved at the output of the 8 summing channels

Am

plit

ude

[V]

Time [A.U.]

New APD FE electronics

Improved PCB layout (better separation of Analogic and Digital grounding, lower coupling even if higher bandwidth- about 20 MHz)

New components instead of ones that have shown failures. Control bus (I2C) improved

New FE Board Old FE Board

Electronics production and commissioning actual schedule

Design of the new electronics in Dec.09 Prototype and test: Mar.09 Component procurement and PCB production: Apr. 09 Delay in delivery and bad production. First 32 channels at the end of

July and second 32 channels in a second production at end of august. Mounting and commissioning:

TC US 1st week of August, TC DS 1st week of September.

Positive stand-alone tests before entering in COBRA. Due to the tight mounting schedule and the priortary DAQ tuning before

starting stable data taking, we were forced to skip the full integration test with DCH inside COBRA. Test were made only accessing the electronics outside COBRA.

First TC Full operating test with DCH: found a not strict correlation with DCH noise from APDs US/DS

From Run 50225-50358 APD ON, From Run 50359 APD off for DAQ problem From Run 50506 APD ON From Run 50590-50659 APD ON -> DS OFF-non effect -> US off noise disappear

APD DS OFF

APD US OFF

APD ON

APD OFFDAQ Problem

APD ON

?

Katia F.

Comparison with Run2008 Effect of APD on the DCH in run 2009 of old electronics From run 38104 al run 39349 gli APD OFF, in the remaining runs APD ON. Negligible effect on DCH

APD OFF APD ON Katia F.

Negative results acting outside COBRA

KatiaAPD ON

A full survey of all possible sources of noise/EMI outside COBRA results with no improvement: conditions of stable performance were not achieved

Need of working directly on the TC on-Board electronics → wait for the shut-down

APD OFF

Work under way in Jan.-Mar. Level of EMI/noise signal at the input:

20-50 uV if not coherent, 3-6 uV if coherent.

Due to high amplification: 0.1-1 V signal on output cable--> possible irradiation to DCH Positive feedback if input couple with outputs

Work planned with the US and DS TC:1- test an EM shielding on the preamplifier input2- test the effect of pick-up on HV and LV cable3–reduce the cable emission inside COBRA

4- eliminate any cause of coupling of the output to the input5- change the not working boards and  a few resistors on I2C bus receiver

Test the effect of these changes with the TC inside the COBRA.

Two phase work:1-the first just after the Xtmas holidays (jan 11 to 29) in order to find the causes of the excess noise and study/test the solutions2-the second period after a while in order to have enough time to build the shielding tool in our workshop (2nd half of February)

1St Phase done Balanced the I2C bus from Pacth Panel to F.E. boards (change of pull-up

resistors) → now bus signal in the specifics in any conditions and stable when idle

Inserted a shield on to APD-Preamplifier input → decoupled input from EMI and HV or output (digital or analogic cables)

Reduced the analogic output band from 150 Mhz to approx 50 MHz with further feedback capacitor → reduced the capability to emits high frequency signals

Decoupled differential amplifier output from twisted pairs cable with small resistor (60ohm/polarity) → reduced back action from electronics rack

Reduced HV- output coupling by choosing different cable paths and proper shielding → output signal decoupled from FE input through HV cables

Burst signals generated by HV where filtered ( do be done properly later) Improved Power supply of F.E boards by changing cables from Patch Panel

→ decoupling of different F.E. Board respect supplied by the same Patch Panel

Few snapshot of the work under way

Shield of APD-Preamplifier input

Decoupling HV-input-output

Test of improved supply sables

Insert 2 capacitors, change 1 resistorInsert 2 output matched resistors

Before/After (few examples)

Typical EMI from HV HV filtered

HV-20MHz BW

Out

HV-500MHz BW

Out

I2C with high freq oscillationafter the transmission

Clean I2C transmissionPattern and stable aftertransmission

Example of self-sustained and/or picked-up oscillations 100MHz, 20 MHz, 8.3 MHz oscillations were observed but not found a clear origin

Most probable conclusion: mix of picked-up signal that were amplified and sustained by electronics through output-input coupling inside COBRA.

100 MHz 8 MHz

Effect on the DCH noise: at the beginning of the 1st phase test

Out off In off

In on

In off

} Various Groundingand filtering configuration

Effect on the DCH noise: at the end of the 1st phase test

Out

off In

off In O

n

part

ial

In O

n p

art

ial

init

.In

On f

ull

not

init In O

n f

ull

init

Presently achieved an average noise RMS of 25 mV as in the APD test with standalone electronics at Genoa and PSI (outside COBRA), Aug 09.

Conclusions

The goal of the 1st Phase beam-off has bee achieve successfully. After working on shielding, filtering and signal matching, we are

now at the target performance of APDs in operating conditions inside COBRA.

Negligible effects on DCH noise. We need to perform these modifications for all channels and both

TC in the next month Most of February needed for preparing these modification

(shields, cables, filters on HV,…) Completion of work: end of March 2010