1 / 17

HBD Commissioning

HBD Commissioning. Itzhak Tserruya DC meeting, BNL, April 11, 2007. Outline. Noise Gain Response to hadrons: FB vs RB Hadron blindness Event size Gas monitoring Diagnostics and Repair work. Noise. Was excellent in all 24 modules Recently found large noise in 2 modules (WN1 and WS3):

john
Télécharger la présentation

HBD Commissioning

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. HBD Commissioning Itzhak Tserruya DC meeting, BNL, April 11, 2007

  2. Outline • Noise • Gain • Response to hadrons: FB vs RB • Hadron blindness • Event size • Gas monitoring • Diagnostics and Repair work

  3. Noise • Was excellent in all 24 modules • Recently found large noise in 2 modules (WN1 and WS3): • Noise appears only above ~ 3000 V • Does not depend on mesh voltage • Induce noise in other 2 modules in same HV box. • Does not look like real sparking or ground pickup noise. • Noise looks like real signals • Seems to be coming from inside detector

  4. Normal module

  5. One of the two noisy modules

  6. Tracking, position resolution, gain Run 226502 ES4 at 3600V FB Hadrons selected in central arm projected onto HBD Gas gain: (assuming a primary charge of 19e in the 1.5mm drift gap and a conversion of 10 ADC counts/fC) G = 2900 • Much larger than expected • Mostly single pad response • as expected • Position resolution as expected of the order of a cm dictated by the pad size

  7. Hadron Blindness- FB vs RB response Spectra Comparison in FB and RB (for the same number of central tracks) Results very similar to those previously obtained in lab tests or beam tests

  8. First look at electrons in FB Run 226502 ES4 at 3600V FB Electrons selected in central arm projected onto HBD Clear difference with the hadron response. Need much more data for a quantitative analysis.

  9. Event size • The event size is too large and limits the DAQ archiving rate at least in the first half of the store when the luminosity is large. • Noise cannot explain this large event size. • We observe the expected decrease of PH, and consequently of the rate, while operating in RB mode. But this is not reflected in the overall event size. • Suspicion that there is a large background not track related that dominates the event size. • For the moment we are collecting data with only a few modules such that the DAQ is not affected. • Possible cures of the problem: • switch on the HBD gradually as the store luminosity decreases. • record only the time samples of interest. Could gain a factor of 2. Not this year • use one fiber per module instead of one fiber per 2 modules. We could operate as many as 12 modules which is close to the number of operational modules.

  10. HBD IN HBD W ~30 % Loss HBD E ~30-40 % Loss Gas monitoring – 2lpm Flow 2lpm • 30% loss should correspond to 80 ppm of water. However, according to the hygrometer the detector is at app. 12 ppm. Origin of discrepancy not understood. • Working assumption: the gas monitoring results are correct. At the present flow of 2lpm we are loosing 25% of the UV photons. • We asked Rob to increase the gas flow by a factor of two.

  11. Gas monitoring – 3.5 lpm Flow 3.5 lpm

  12. Why is the gain so high? • All modules installed in the HBD show a much higher gain than previously observed in lab measurements. • A lower HV by approximately 200 V is required to achieve the operating gain of 5000. • 3 GEMs randomly selected from the spares were tested recently and show the normal gain curve. • The only differences: • CsI • Dryness • Different gas

  13. HV problem: facts • Frequency of trips much higher than ever observed in the lab. • Most trips are harmless • Massive trips have caused most of the damage. • Mesh to top GEM • Negative dI resulting in over-voltage • Magnet trip • Sensitivity to magnetic field changes

  14. Diagnostics of HV problem • New endurance test at WIS – done • Test CF4 gas from the present batch used in the run at SUNY • Check possible effect of magnetic field on the mesh – no effect • Manufacture transparent side cover • Before disassembling West detector: • Replace side cover with the transparent one • Induce trips • Test effectiveness of shadows in preventing massive trips

  15. New Endurance Test • exactly the same powering scheme used in the installed HBD • no sparks in almost 2 weeks • gain curve very similar to those measured in many previous tests • Very different from gain curves of the modules installed in the HBD

  16. Repair work at WI • Procurement of GEMs and frames: • order already placed • expect first GEMs by the end of the month • total delivery time 6 weeks • GEM assembly, test and shipping for first arm: 6 weeks • GEM assembly test and shipping for second arm: 6 weeks Total: 18 weeks

  17. Repair work at SUNY • Diagnostics of HV problem: 6 weeks • CsI evaporation, test and assembly West arm: 6 weeks • West arm gas flow and CF4 test in the lab. 6 weeks • Same for East arm: 6 weeks Total: 24 weeks If we want the detectors back at BNL in Nov. 1st for run 8, we must take the West arm out not later than May 1st. Working hypothesis: access on April 25 is the target date to take out HBD west, pending progress on the preparations at SUNY and collecting enough data with the two arms.

More Related