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Preliminary Results from a Trial Beam Test of the Small HBD Prototype at LEGS

Preliminary Results from a Trial Beam Test of the Small HBD Prototype at LEGS. Bob Azmoun BNL HBD Working Group Meeting May 10, 2005. LEGS Cherenkov Counter w/ ~2” Lucite. Veto pulse height Spectrum. ~50cm CF 4 Radiator. H1. 3x3 pad array (3x3cm ea.). S1. S2.

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Preliminary Results from a Trial Beam Test of the Small HBD Prototype at LEGS

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  1. Preliminary Results from a Trial Beam Test of the Small HBD Prototype at LEGS Bob Azmoun BNL HBD Working Group Meeting May 10, 2005

  2. LEGS Cherenkov Counter w/ ~2” Lucite Veto pulse height Spectrum ~50cm CF4 Radiator H1 3x3 pad array (3x3cm ea.) S1 S2 1 e- 2 e- 3 e- Tagged ~2 GeV e- Beam SS Vessel The spectrum depicts single, double and triple particle showers passing through the veto scintillator. Retractable VUV Lamp Retractable Fe-55 Veto CsI 3-GEM 64 Ch. e- Hodoscope LEGS e- Tagger Cave Test Beam Layout • The beam was studied extensively, so that the apparatus could be precisely aligned. • Trigger = H1+S1+S2 • Veto Cut Applied Off-line (although ~95% of e-’s are vetoed, this Veto provides for a very clean e- trigger, and removes all tracks that have associated showers, produced somewhere along the e- trajectory) Bob Azmoun, BNL

  3. Water “peaks” Gas Quality Before and After Test Expect ~34pe’s • The Vessel was pumped on for two days, and purged for ~two weeks before the test • The simple gas sys. (gas cyl.+flow-meter+bubbler) used for the test was purged at high flow for two days. The det. was sealed and transferred to LEGS, attached to the gas sys. and purged for ~5 hrs. • There were no means to test the gas quality during the test, however we did test the gas quality before and after the test, under more or less the same conditions (i.e., similar purging period and flow rates). Bob Azmoun, BNL

  4. GEM PC QE Measurement Three Weeks Before Test Ratio of the Area under each (Red/Blue) trend line = 2.0 • The last time the GEM PC was measured, its integrated QE was half that of the nominal value. • Degradation in the PC may have been due to handling and/or method of storage. • GEM PC was stored in questionable conditions after its QE was measured (sealed vessel filled with N2) for two weeks prior to the test. Thus, the QE may have suffered some additional deterioration than what is suggested in the plot above. Bob Azmoun, BNL

  5. Photoelectron Coll. Efficiency Vs ED • Forward Bias: ED= +1.2kV/cm • Reverse Bias: ED= -0.3kV/cm  ~ 0.9nA/1.0nA = 90% coll. eff. Bob Azmoun, BNL

  6. Gain measurement Before During and After Test • The GEM was operated with the WIS Volt Divider w/ Vin=4200, which • corresponds to a Gain ~ 5700 (as measured at LEGS, using Fe-55). Bob Azmoun, BNL

  7. All 9 Pads: ED = +1.2kV/cm Central Pad: ED = +1.2kV/cm, Veto Cut <ne-> ~51.5e-’s • Expected primary charge from dE/dx: • dE/dxMIP= 7keV/cm * 2.44mm / (54eV/e--ion pair) • = 31.6 e-’s • For ~2GeV e-’sRelativistic Rise factor: • 31.6*1.4 = 44.3 e-’s • Measured primary Charge from dE/dx: • At Gain of ~5700, Landau Mean ~ 51.5e-’s • (total chg. Pad 5) – 7.9pe’s (Cherenkov Pad 5) = 43.6 e-’s • This result is derived from a “Quick Analysis”,where the Landau mean was roughly approximated…a more rigorous analysis will be done shortly Bob Azmoun, BNL

  8. All 9 Pads: ED = -0.3kV/cm • Mean number of Cherenkov pe-’s measured: • Instead of adding pulse heights event by event • for all the pads, a rough approximation of the mean • number of total photoelectrons is calculated by • summing the mean pulse height for each pad…a more • rigorous analysis will be done shortly. • The SUM of the avg. number of pe-’s contributed • from each pad = 18.5pe-’s (Gain=5700) • The SUM in this calc. is an overestimate of the same number calculated event-by-event, and so may be taken as an upper limit. • Correcting for known Detector Inefficiency’s • 6% loss of primary pe-’s due to absorption in gas • Integrated QE is low by a factor of 2.0 • pe Collection Efficiency ~90% • Corrected # of pe-’s • = 18.5pe * 1.06 * 2.0 * (1/0.9) • = 43.66 pe ! (upper limit) • (Remember, this is a rough approx.) • The final measurement shows a lot of promise! <npe> = 2.3 <npe> = 2.0 <npe> = 1.2 <npe> = 7.9 <npe> = 1.7 <npe> = 1.0 <npe> = 0.9 <npe> = 0.8 <npe> = 0.8 Note: The data presented in the histograms above is not the data set that was analyzed, and is meant to give an overall qualitative idea of the data, rather thanact as anexactreference. Bob Azmoun, BNL

  9. Next, Full Scale Test will include… • GEM PC with nominal QE • Need Large Glove Box to accommodate Det. for • installation of CsI PC • Water and Oxygen Analyzers • Ordered New Panametrics Analyzers (arriving shortly) • Utilize Flash Lamp During Test to test the PC, • and/or the gas transmittance. • The Test is scheduled to take place either this • June or July Bob Azmoun, BNL

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