Searching for the QGT : Q uantum Efficiency G ain T ransparency

1. Searching for the QGT:Quantum EfficiencyGainTransparency TK Hemmick for the HBD Crew

2. Overview • HBD Prototype Status • QE; Gain; Transparency • Electronics • Preliminary Run Plan • Delivery; Cuddy Tests • Zero Field; +/- Field • HBD Construction Status • Vessel; PCB; Glove Box

3. Summary in Brief: Quantum Efficiency. • The GEM was evaporated on Monday April 3 • The Local QE test looks basically normal (a bit above average) • Flash Lamp tests same today as initial installation: • April 6: 475 mV in CF4 (only 6.7 turns of detector) • April 10: 514 mV in CF4

4. Summary in Brief: Gain • A number of gain curves weretaken prior to replacing the grid. • One anomalouslow-gain scan wasseen (detail later) • With grid replaced and operating via a resistor chain the SUPER WEAK source still shows 55Fe peak. Present State

5. Summary in Brief: Transparency. • Levels presently in HBD prototype: • 14 ppm water. • 22 ppm oxygen. • Presently low flow to conserve CF4 • Easy to achieve < 10 ppm each… • Water cost in photo-electrons: • ~1 p.e./ 10ppm of water

6. Collage of Process. • Status: • Grid Corona repair success. • 4 bad strips on top GEM…Live with it. 55Fe

7. Prototype Summary: • HBD ready for installation. • Few Troubles Encountered: • Corona point on grid…found and fixed. • 2 Shorted Strips…compensated via divider chain. • Shorted strips only 4% of GEM area. • We will monitor QE and Gain daily: • Use existing as long as it continues to work. • Backup photo-cathode ready (if needed). • Chi sees running compressor FPGA code. • Expects to be ready by install date (April 19) • “Shotgun Wedding” of detector to electronics.

8. Option 3 Preliminary Run Plan • Ship Monday April 17. • In assembly hall by Tuesday afternoon. • Install during Wednesday April 19 access. • Initial install below beam pipe (turtle mode) Option 1 Option 2

9. Turtle Position Tests • CUDDY HUTCH TESTS: Oscilloscope(Signals are coming from HBD...) • Look for 55Fe signals on scope. • Look for MIPs on scope + digitize. • FULL CHAIN TESTS-1:  STANDALONE DAQ(Signals are getting through DAQ...) • Establish throughput of data in separate granule. • Use MIPs to perform "gate timing". • Use laser trigger to flash our lamp as well(??) Move detector to operating position after MIPs are seen though full chain NOTE: Detector can switch from hadron-sensitive to hadron-blind by changing grid bias.

10. Operating Position Tests • FULL CHAIN TESTS-2:  STANDALONE DAQ(First observation of Cerenkov Blobs...) • Double check timing of signals with grid in "MIP mode". • ZERO the magnetic field. • Put detector in Blind-Mode and take ERT triggers: • FULL CHAIN TESTS-3:  BIG PARTITION(Blobs from identified electrons; N-zero) • ZERO the magnetic field. • Set detector to Blind-Mode and take ERT triggers • Use DCH/RICH/EMC to select events with an electron in the HBD active area. • FULL CHAIN TESTS-4:  PLUS/MINUS FIELD. (Matching/veto power in field on mode...) • Swap the leads on the magnet for +/-. • Take another zero-field reference run. • Take 1/4, 1/2, 3/4, and full field runs. • Scan the middle coil above and below the "cancel point“.

11. General Questions/Issues • Can we get an ERT trigger that shadows the HBD active area? • Should be possible by masking off channels that do not shadow HBD active area. • Can we get a LVL-2 trigger to run that selects electrons in the HBD active area? • Not needed if masking ERT channels. • Desirable if ERT is unchanged during “our” runs. • Is our present offline software optimized for debugging the detector? • Tracks do project into HBD, clusters are formed. • Initial calibration is issue (MIPs??) • Do we want to use the flash lamp in a manner like the EMC laser trigger? • Possible in principle if we get trigger to lamp. • Value is debatable during Run6 (better in Run7…)

12. Main HBD: HV panels and side covers Gas in/out ports UV window ports Inner side Bottom Top Brackets inserts Voltage dividers Outer (copper) side

13. Jig #1 for the PCB and active panels

14. Jig #2 for the entire vessel • Main HBD is ready with only the exception of the Kapton PCB that carries the pads.

15. Update on the PCB production • There were problems at each of the three production steps (drilling, plating, etching) and three production cycles were needed before one full cycle could be completed. This happened on March 30. • Ilia traveled to Geneva and brought the PCB to WI on March 31. • A thorough check of the PCB revealed two problems: • 172 holes (app. 15%) were not plated-through • app. 50% of the holes for the pins to support the GEMs were not at the correct place. We could mount the pins of three panels only, the rest was increasingly off (maximum deviation is of the order of 1 mm) • A thorough comparison with the PCBs that failed in the previous cycles revealed that the material suffers some contraction mainly during the plating process but also during etching. • CERN is producing a new PCB introducing a scaling factor in the drilling that will hopefully compensate for the contraction. • In the meantime we have developed the tools and means to repair the existing PCB, in case that this new cycle would turn out to fail again.

16. Hole mismatch Bottom Right Bottom middle

17. Glove Box • DELAY!!! • Installation of Glove Box on May 30/31. • Difficult to imagine using it for a beam test using partially instrumented final HBD. • CAN use Italian box (we just did this…) • No presently known advantage of final HBD over present state of prototype. • No desire to compromise final detector to rush pieces into beam.