Timing Counter Report of Feb 20th, 2008 F.Gatti

Final Construction Phase of TC TC with fibers exposed TC upside down for Fiber APD gluing High reflectance polymer foil coating TC before insertion in COBRA Cables and pipes of TC in COBRA before final positioning

TC/Bag final positioning TC COBRA BORE +15 mm from nominal position Bag SS inner edge COBA inner step DCH supports Bag SS inner cap Bag EVAL inner side backside illuminated PM at the final position inside bag

Fibers detector Fibers detector “turned on” The analog output achieved a good S/N level that has been tested channel by channel. A selected event of a CR that hits at least 3 fibers is shown as example 8 Channels analog sum 8 Channels analog sum Signal of 8+8 Interleaved fibers 8 Channels analog sum

Timing Analysis Use positrons runs with TRIGGER on TC only (2 or 3 contiguous bars in coincidence). Reference data: 250k triggers belonging to #8378-#8408 runs Measure bar average time T k First method:  ( T k - T k+1 ) ≈  ( s/c  T  Second method:   (T k +T k+2 )/2 - T k+1  ≈  ( 0+  T  BC A e + A s

No cuts timing analysis: 3 bars example Higher order effects Correction for the first two bars used

No cuts timing analysis: all bars Bar1–Bar0 Bar2–Bar1 upstreamdownstream Different chip

Searching the intrinsec timing resolutions The methods give z-dependent results  low z cuts give better resolution  not fully explained by MC and presently under study Time reconstruction from digitized pulse are affected by the electronics/algorithm intrinsic jitter  evaluation of this time jitter has been done in a dedicated run. Double Threshold Discriminator pulse is available to overcome the elctr./alg. jitter

Z-cuts Timing Analysis with DTD and PMT pulses Bar3 - Bar2 PMT DTD Time resolution  = 52 ps DTD Bar3 - Bar2 Cuts: 0.1V<pulse height<0.3V (Landau peak) Reconstructed z on first bar < 55 cm PMT Time resolution  = 62 ps

Intrinsic electronics/algorithm jitter in PMT signal Dedicated positron runs: one PM signal feeds the two input channels of the corresponding bar:  same signal to the two electronics chains of the bar.  Time distribution only affected by electronics/algorithm jitter It has been measured   T 1 -T 2 )= 2  ( T 1 +T 2 /2 )) Average jitter value= 54 ps Final PMT timing resolution after elect/algor. jitter subtraction  55 ps rms  129 ps FWHM DTD analysis gives 120 ps FWM without jitter correction. Latest preliminary results Latest preliminary results on DTD after jitter correction: 108 ps FWHM Runs Runs

First comments on time analysis DTD pulse analysis method shows better performance in the first analysis (not all correction applied as in PMT signal analysis). PMT and DTD give us good redundancy for the timing of a single event. Corrections for the time-walk, hit position, electr./algorithm jitter, systematic of the timing resolution analysis methods, are under study. Z dependence of T resolution under study (MC vs data comparison): the effect suggests a dependence of the chosen timing method on track inclination (low Z  low impulse z projection). 120 ps FWMH Finally the TC intrinsic time resolution in operating conditions is now evaluated to be 120 ps FWMH (20% excess respect to the proposal), 108 ps FWHM Latest preliminary results show 108 ps FWHM jitter corrected DTD signal. We are confident that there is room for the fine tuning of the timing analysis and a further assessment of the of the timing resolution

PMT equalization ( CR and CW data) Black: CR run Red: B run Green: LiF run

Charge Analysis V eff : measurement of positron impact time on the bar, T measurement of z can be made, in principle, from the width of the t 1 -t 0 distribution Measurement of z with the charge, once that eff is known  need  ( v eff )/v eff ~1% to achieve the desired T resolution eff : independent measurement of z can be measured from: - ln(Q1/Q0) vs z determined with time once that v eff is known - ln(Q1/Q0) using z measurement from fibers

eff. and Veff. Significant differences among bars, consistent with results at BTF. Data suggests not uniform losses in the internal reflection: - residual surface roughness (measured value lower than 0.2  m RA) - plastic enclosure residual reflectivity  Effective velocity: 14.5+/-0.2 cm/n Black: CR run Red: B run Green: LiF run eff

Laser for 532 and 266 nm monitoring pulse The system delivered during the run. Now under test with the optical fiber distributor Power stability at 48 MHz, 1064 nm, within 0.3% over a week of monitoring Timing pulse distributed via optical fiber and detected on TC DS at 50 Hz free running repetition rate 3m cavity 48 MHz, 1064nm Diode pumped Nd:YVO Acustic-optical pulse selectors 50 Hz 2 stages pulse amplifier 532nm 256 nm To fast APD for power and int.pulse sync To opt. fiber and fast APD for trig. Out.

Laser Status Laser assembly and table under integration before transportation at PSI

Preparation for the run08 Mostly done last week Completion of the commissioning of the digital hit map for the fibers with CR (Mostly done last week) Works on TC: change of PMTs with unexplained low gain, close light leak in the APD fibers detector, change not working APD boards, improve S/N and noise immunity of the APD analog output Improvement of the S/N will allow to decrease the threshold level in trigger algorithm  recover some delay (20-30 ns ?) in the trigger latency Rebuild N2 Bags Integrate the Laser for TC and XEC

Question of shaping time of APD electronics The 160 ns shaping time (10-90%) + the latency of the trigger APD algorithm prevented the use of the in the on line trigger selection in the run07 An anticipation of about 60 ns of the formed trigger signal from APD should be enough ton solve the problem Improvement of the S/N will allow to decrease the threshold  recover some delay (20-30 ns?) From the trigger side it is possible to reduce the processing time of the algorithm.  APD online in the trigger for Run08 Alternative possibility of reducing shaping time for 512 channels is not a trivial task and requires 7 weeks of with 6 people. This could be done eventually at the end of the run 08

Last on PMT life The measurement lasted 290 days for a total current of 2130 Coulomb on a new PMT The average current produced by the PMT over the period has been 88,2 microA Data presented has been already corrected by the laser power variation with the photocell values

Previous measurements on old PM Drift region of the old 1-1/2” PM lifeG/G(0) 0.290% 2.077% 3.370% 5.065%

New measurements: 6.6 x life without changes

Schedule

End of slides

backup  MC  T-data

backup

Backup T1= t0 + x/c T2= t0 + (L-x)/c T1+T2= 2 t0 + L/c TA=(T1+T2)/2= t0 + L/2c TB=t0+s/c+ L/2c TA-TB = s/c s/2 TA+TB=2t0+s/c+(L/c) TC=t0+s/2c+L/2c (TA+TB)/2-TC= t0+s/2c+L/2c-t0-s/2c+L/2c=0 A C B s/2