Construction and First Results of a Cosmic Ray Telescope

1. Construction and First Results of a Cosmic Ray Telescope M. P. Belhorn University of Cincinnati 12 June 2008

2. Cosmic Ray Telescope Why? • Testing and Triggering of a focusing DIRC prototype. • The combination of a CRT and fDIRC will allow a more accurate study of focused rings than not. • Specifically, the CRT provides track trajectory information that influences the ring image and can be used to optimize focusing.

3. Cosmic Ray Telescope Why? • Testing and Triggering of a focusing DIRC prototype. • The combination of a CRT and fDIRC will allow a more accurate study of focused rings than not. • Specifically, the CRT provides track trajectory information that influences the ring image. • Studying the behavior of potential fDIRC components. • The CRT will use several of the components that might be used in the actual fDIRC.

4. Cosmic Ray Telescope Basic Design The CRT is an orthogonal scintillating optical fiber particle detector. Four sets of scintillator impregnated optical fibers form ribbons that are held in an Al chassis. Two groups of ribbons, each consisting of two sets stacked vertically above each other, are arranged 90 degrees w/r to each other. Light detected in each fiber due to >MIP give two x-y coordinate pairs that specify the particle trajectory.

5. Cosmic Ray Telescope Basic Design CRT is triggered by scintillating paddles in coincidence. Light is detected by 2 64-anode PMT arrays (Hamamatsu H8500) The signal is processed by compact amplifier/discriminators (PS 6816) The logic output of the PS6816s is checked for trigger matching via 128 channel TDC (Caen V1190A) TDC is readout via VMEbus/USB to host PC. (Wiener P&B VM-USB)

6. Cosmic Ray Telescope The Scintillating Fibers The fiber groups consist of 64 1x1 mm^2 Bicron BCF-10 scintillating fibers. Ribbons are then ~32 mm wide. They are separated vertically by 115 mm. The device as a whole has an acceptance cone of ~15 degrees measured from the azimuth. The resolution of a single track is Arctan(1/115)≈0.5 degrees.

7. Cosmic Ray Telescope The Chassis • The chassis was designed to: • Locate the fibers in space to specifications • The fibers were ordered before chassis design was determined. • Acceptance cone was preset. • Shield the fibers from external light sources • The fibers are only coated in a 15 micron thick EMA to prevent cross-talk • Shielding compromised on fibers during fabrication • Support the detector electronics

8. Cosmic Ray Telescope The Detector Electronics Scintillation light is collected by 2 H8500s. We have both a first generation and latest generation H8500 that allows us some first hand comparison between the two for use in an fDIRC.

9. Cosmic Ray Telescope The Trigger The CRT is triggered by 2 stacked scintillating paddles. We can change the minimum momentum of the particles observed by placing attenuating material between triggers (i.e. 40cm of iron) The paddles’ output is sent to a NIM crate for logic testing

10. Cosmic Ray Telescope The Trigger First, 2 discriminator modules (ORTEC 473A) pass a NIM logical high if the PMT signal is above threshold

11. Cosmic Ray Telescope The Trigger Discriminator logic outs are then compared for coincident signal rises (with 5ns). If true, NIM logic high is passed to delay generator

12. Cosmic Ray Telescope The Trigger Delay generator moves trigger time to a better location for the TDC. Outputs 2 ECL logic highs. One triggers TDC, the other…

13. Cosmic Ray Telescope The Trigger … increments a scalar counter for diagnostic purposes.

14. Cosmic Ray Telescope DAQ The signals from the H8500s are fed through 8 16-channel combination amplifier/discriminator cards (Phillips Scientific 6816) The output of the 6816s is differential ECL logic highs and lows that are fed into the Caen V1190A 128 channel TDC.

15. Cosmic Ray Telescope DAQ The TDC operates on a VMEbus and can be communicated with via the VM-USB VMEbus controller over USB.

16. Cosmic Ray Telescope DAQ The TDC operates on a VMEbus and can be communicated with via the VM-USB VMEbus controller over USB. This device is amazing.

17. Cosmic Ray Telescope DAQ The TDC operates on a VMEbus and can be communicated with via the VM-USB VMEbus controller over USB. This device is also a headache

18. Cosmic Ray Telescope DAQ The TDC operates on a VMEbus and can be communicated with via the VM-USB VMEbus controller over USB. Much of the time spent on this project was devoted to writing software to control this unit.

19. Cosmic Ray Telescope DAQ The TDC operates in a “trigger matching mode” where all hits that occur within a programmable time window are collected and sent to an output buffer that can be dumped to the PC via USB2. The TDC has a timing resolution of 100 ps, a 5ns channel deadtime after measurement, and it searches for signal leading edges. Analysis of the output of the TDC was done in Mathematica.

20. Cosmic Ray Telescope First Results Initial calibration set by taking long data set and looking for “perfect” events: A perfect event is one where there are exactly four hits within a reasonable time, one on each set plane. These rare events allow us to determine the time delay for signals on the same PMT (avg. of 1750 ps for PMT A and 700 ps for PMT B) These events also help set narrow the initial time matching window.

21. Cosmic Ray Telescope First Results Most of the triggered events are junk.

22. Cosmic Ray Telescope First Results Although early data gives give great information regarding the operation of the CRT. Especially timing information.

23. Cosmic Ray Telescope First Results More timing information.

24. Cosmic Ray Telescope First Results Still more timing information.

25. Cosmic Ray Telescope First Results Early data also gives information on channel triggering rates, and dead channels.

26. Cosmic Ray Telescope First Results There is something amiss about the channel thresholds. Our next largest goal is to fine tune the thresholds.

27. Cosmic Ray Telescope Conclusions • We have an operational CRT. • Next issues to address: • Fix bad amp./disc. Channel. • Optimize thresholds. • Stiffen track triggers to reduce noise. I would like to acknowledge: R. Johnson, R. Schrott, M. Ankenbauer, A. Ruben, J. Whitaker, and especially A. Schwartz, J. Markus, and R. Gass for their assistance in all of this project.