Status of Oxford Setup Matthew Chalk, Erik Devetak, Johan Fopma, Brian Hawes, Ben Jeffery, Nikhil Kundu, Andrei Nomerotski University of Oxford ( 18 August 2006 )

2 Oxford Test Setup Goals  Fully test and exercise produced electronics, should improve understanding, quality and feedback  Analogue readout of CPC2  Perform additional CPC2 measurements, build up CCD expertise  Experiment with power provisions for the clock driver with real sensor and super-capacitors

3 Oxford Test Setup Light version of the RAL setup

4 Status Minimal configuration is functioning  Sequencer based on BVM2  Agilent LV PS  Oxford Bias PS controlled by BVM1  Agilent mixed-signal Oscilloscope used as ADC  LabView code was mostly inspired by RAL examples Many thanks to Konstantin for help Main parameters  Sequencer Master Clock: 1-10MHz  Integration time (time between triggers) sec  Graph: RG, CCD Clock and CCD analogue readout

5 Measurements: X-ray signal Standard procedure : to enhance probability to have a Fe55 signal need to integrate long time  need to operate at low temperature Our setup is running so far at room temperature  accumulate substantial noise from leakage current Reduced integration time to minimum (3 msec) and used accumulation feature of the scope Background noise Signal (approx. 15mV below the noise ) N.B. Picture taken straight from the oscilloscope

6 Measurements: X-ray signal RMS of Raw Noise : 2-4 mV Illuminated CPC2 with Fe55 X-ray source (5.9 keV) Signal : mV  useful calibration  18 mV expected based on expected amplification etc  1600 e from Fe55  ~100 e / mV  Noise ~300 e (to compare to e at RAL – ways to go!) Noise performance is poor as expected at room temperature and long integration time Had a setback using the ICS-554 PCI ADC  Double PCI-PMC carrier does not fit in our PC     Will exchange for a single carrier, here in a month  Potentially ICS-554 will allow fast readout (faster than VME), it also has onboard large FPGA for pre-processing so further speed-up is possible (for ex setting a threshold and passing on to the PCI bus only events above the threshold) In the meantime tried to detect signal using scope trace readout to PC but this was too slow Concentrated on noise measurements

7 Noise Analysis Examples on noise graphs Different pixels have different offsets (pedestals) Software subtracts pedestals so many rows can be added up (right bottom graph)  Almost no tails in noise distribution  good fit by single Gaussian

8 Noise vs Integration Time Naively expect that leakage current is main noise contributor  N carriers ~ T integration  Noise ~ sqrt( T integration ) Trigger rate effectively determines integration time See some dependence above 100 msec, no dependence below It looks that at smaller integration time noise is not caused by the leakage current  room for further improvement?

9 Noise vs Master Clock Frequency Higher frequency effectively decreases integration time so this qualitatively agrees with previous result

10 Noise analysis To explain better what we measure: Scope traces include 50 consecutive pixels (so 50 rows of CCD) These 50 rows can be sampled at any location of CPC2 Simultaneously 3 CCD columns are measured, see graph Amplitude for each pixel is measured at a certain delay wrt trigger Can study noise correlations between CCD rows and columns

11 Noise correlations Dnoise = standard deviation of amplitude difference for two channels  If no correlation expect Dnoise to increase by sqrt(2) wrt noise of single channel  If absolute correlation expect Dnoise to be 0  If absolute anti-correlation expect Dnoise to be doubled Can study  Column Dnoise – expect correlation as readings are taken simultaneously  Row Dnoise – expect less or no correlation as rows are read out at different time

12 Column Dnoise Took data for 12 locations : 4x3 columns with analogue outputs times 3 row regions Adjacent column Dnoise: A ij – A i +1 j Noise ~ 2 mV  Assuming no correlation between pixels   2mV/1.4*100e/mV = 140 e Uniform column Dnoise across CCD

13 Column Dnoise Correlation of far away columns Far away column Dnoise: A ij – A i +N j Less correlation with far away columns

14 Row Dnoise Adjacent row Dnoise: A ij – A ij +1

15 Row Dnoise Far away row Dnoise: A ij – A ij +N Limited by 50 pixel readings (scope) Results suggest anti-correlation Need further study – a bit controversial measurement

16 Summary Oxford setup is up and running So far studied CPC2 noise at room temperature Setup was very useful for MB4.3 debugging – hopefully goes to RAL in better shape than previous versions Plans  Lower temperature  Set up proper ADC readout  Study signal response  gain calibration etc  Set up charge injection mode