1. The Pierre-Auger PMT Test Stand Chris Jillings Feb 6, 2002

2. Lest anyone think these are all my ideas… Thanks to –Professor Arisaka –Arun Tripathi –Jonathon Kubic –Tohru Ohnuki –Professor Hauser –Several others

3. Pierre-Auger A cosmic-ray observatory Primaries with E>10**20 eV Calorimetric tanks in Argentine pampas

4. Concept of Auger Hybrid Detector Fluorescence Detector Surface Detector (Water Tank) PMTs

6. Tanks Shower particles hit tanks Emit Cherenkov light in water Cherenkov light detected by three PMTs

8. PMTs Photonis XP1805 PMTs

9. Expected range of PMT signals Need to observe single muons for calibration. Also need to be able to observe showers with energy up to 10 21 eV. Based on simulations, we need to be able to observe from 50 to 50,000 pe/25 ns. –Linearity over a large range of anode currents required.

10. Auger Electronics Huge Dynamic range –15 bits LSB = signal from 1 photoelectron PMT must be linear

11. Auger PMT requirements Good quantum efficiency in 350-450 nm range. Standard operating gain of 2x10 5 (to match the FADC dynamic range to expected signals). Good linearity up to 50 mA anode current (corresponding to the largest expected signal). Dark pulse rate < 10 KHz. Afterpulse ratio < 5% (200ns-5000ns from main pulse). Rise time < 10 ns. Transit time spread < 10 ns.

12. Linearity If the input light is doubled, is the output doubled? (Integral non-linearity) Have two LEDs –Pulse LED A –Pulse LED B –Pulse Both Is the whole the sum of the parts?

13. Linearity (contd.) Two pulsed blue LEDs run like, A, B, (A+B), A, B, (A+B) …… Non-Linearity is given by deviation of (AB) from sum of A and B.

14. Why this is a good idea Do not need calibration of electronics. Do not need calibration of light source. Do not need to compare against a reference.

15. An example

16. Why this is hard The two LEDs must have no cross-talk If pulsing LED A affects LED B then the system is will not work because the light from A&B together is different than A+B. Grounding

17. Fast LED Pulser 50 2 5 nF 110 TTL 5 nF 50 2 110 TTL

18. LED Control Comp I/O card Comedi Ref V (A) Ref V (B) A B Trigger

19. Digital Control Trigger goes to A, B and read-out. Trigger and A go to AND gate. If A high, trigger passes and LED A pulses. Ditto B. If both A and B low, no light but electronics still triggered: pedestal

20. Analog Control Want high impedance. Use non-inverting amp. + - R1 R2 G = 1+R1/R2 If G is small, will oscillate! Use a Slow op amp: a 741!

21. Part II Testing 16 PMTs at once

22. Linearity Test (again) Dynamic range: to read out on ADC want only 10% of PMT signal But we need all of PMT signal for other measurements! A signal splitter.

23. The Splitter If I could change one thing, it would be the splitter. 10 510 To 50  loads R in = 50 

24. The Splitter 10 510 LeCroy QDC 50

25. LeCroy QDC Inputs Are active They are not: 50

26. The Splitter 10 510 LeCroy QDC 50 Buffer

27. How I would do it next time R R R Buffer Atten

28. PMT HV control DC-DC HV –12 V power –Control ref 0-2.5V Use 32-chan analog output card for computer-control of HV. UEI (www.ueidaq.com)www.ueidaq.com Runs under Linux

29. What worked All the DC stuff Commercial PCI cards (mostly) The light sources

30. What worked with effort Splitting HV control with LeCroy 1440

31. A Proposal Get a good scope with built-in math Make sure the scope talks ethernet or gpib Run the system under LabView Use a relay-switch MUX to look at PMTs in turn.