HBD Status Report

1. HBD Status Report C. Woody For the HBD Crew DC Meeting June 13, 2007

2. Overall Status • We believe we have determined the main cause of the sparking problems with the both detectors: • Normal GEM spark would cause Lecroy HV to trip • Mesh also trips leaving large stored energy on filter capacitor • As GEM voltage goes to zero, large DV develops across gap between • top GEM and mesh, ultimately resulting in a large spark • This spark induces sparks in other GEMs (massive trips) by propagation of scintillation light • There is however a danger in the “One source of all troubles” theory and we are still looking for more possible causes of the problems we had during the run • Status of data analysis • Status of detector reconstruction C.Woody, DC Meeting, 6/13/07

3. Pock Marks • Human eye could see the holes. • Holes smaller than pock parks. • Pocks almost certainly from meshGEM T.Hemmick DC Meeting 5/9/07 C.Woody, DC Meeting, 6/13/07

4. Cluster size from hadrons • Hadrons are expected to produce predominantly single pad clusters • We observe: • a large fraction of clusters with more than two pads • the fraction increases with gain • It is not noise • It is not due to diffusion • It is not coming from tracks with a large incidence angle (checked by restricting “zed” and “phi” in DC) • The multiple pad clusters are created by scintillation. This is supported by: • by analyzing the pulse height distribution of the high vs. low pad amplitude in the cluster • the characteristics of the single pad clusters, not associated with tracks (see next slide).

5. Single pad clusters(not belonging to tracks) • In FB we see two components; • a fast exponential distribution • a slow exponential distribution • In RB mode: • the first component survives entirely • the second is strongly suppressed • Interpretation: the first component is due to scintillation and the second component to charged particles crossing the drift gap not originating from the collision vertex Distribution fitted with: y = p0 exp (p1* x) Inverse slope: 6 ADC counts  Gain 3650 (upper limit) compared to 5850 derived from the mean mip. C.Woody, DC Meeting, 6/13/07

6. Is the Gain of the GEMs affected by the CsI ? • Procedure: • 14 hour gain saturation curve • to fully charge up the stack • waited ~2 hours with voltage on • to verify stable gain • measured gain as a function of dV • corrected for P/T !! • use extrapolated saturation curve to correct for time… • source rate: ~100 Hz **note** the WIS data is from two different stacks… a gem was exchanged. --maybe not comparable. J.Kamin C.Woody, DC Meeting, 6/13/07

7. Question: Is electron attachment in CF4 affecting our apparent gain ? Long drift times of negative ions observed with flash lamp Electron scattering cross-sections in Ar and CF4: elastic momentum transfer (σm), vibrational excitation (σν4, σν3, σνind ), electron attachment (σa), dissociation (σd), excitation (σexc), and ionization (σion). Work in progress ! Collection efficiency drops at very high fields C.Woody, DC Meeting, 6/13/07

8. Taking advantage of the scintillation • The scintillation hits: • provide the best determination of the gain in the detector. • allow an accurate pad by pad gain calibration • allow for accurate monitoring of the gain variation with time (no need for FB dedicated measurements). • How do we define scintillation hit? • Use peripheral events defined by the number of central tracks < 50 • Use single pad hits which do not belong to any track • Assume each hit is a single p.e.  gives an upper limit to the gain (working on a precise determination of the mean number of scintillation p.e. per pad) • Fit the range (10-30) ADC counts with an exponential function • Gain = 1/slope using conversion 10 ADC = 1 fC Scintillation pulse height distribution on a few EN3 pads C.Woody, DC Meeting, 6/13/07

9. Pad to pad Gain variation RB run # 237092, +100V on all modules wrt to nominal • Three types of gain corrections need to be applied: • Pad by pad: should be the same for any run • Module by module: can change from run to run due to changes on HV or dI of a given module • Global gain change due to P/T variations These corrections are essential to distinguish single vs double electron hits C.Woody, DC Meeting, 6/13/07

10. Electron and Hadron Identification Sum of EN3 and WN3 T.Hemmick DC Meeting 5/9/07 C.Woody, DC Meeting, 6/13/07

11. Blocking the scintillation • It seems that we see much more scintillation hits than expected, primarily due to tracks crossing the detector and not originating from the vertex. • This results in a high detector occupancy in more central events that affects the pattern recognition. • Work is in progress to quantitatively understand the amount of scintillation and to block as much as possible of the scintillation light with a system of shades. C.Woody, DC Meeting, 6/13/07

12. Measuring Scintillation in CF4 Preliminary measurement ! Fit to photon yield vs DE gives 140 g/MeV One published measurement gives ~ 250 g/MeV We’re presently setting up to remeasure this in our lab B.Azmoun C.Woody, DC Meeting, 6/13/07

13. Status of GEM production at WIS • 25 Au plated and 30 standard GEMs were ordered from CERN • A first batch of 20 GEMs (10 standard + 10 Au plated) arrived at WI • The production consists of the following steps: 1. 100V test in air (clean room) of the foil before framing 2. 100V test after framing 3. 100V test after soldering SMD resistors 4. 550V test in CF4 in the lab 5. Gain mapping in Ar/CO2 at 484V • So far 15 GEMs (5 standard + 10 Au plated) have been framed, 4 passed steps 1-3, 3 passed full production chain and are in the DB. Only one defective GEM so far. • Production proceeding at about 1 GEM per day • Expect a second and final shipment from CERN by the end of next week. • From last year production we (at WIS) have 16 good fully tested GEMs: 12 standard + 4 Au plated • As soon as the total number of good GEMs will reach 24 (number of slots in the shipment box) we will ship the 1st batch to US. This will hopefully happen in ~1 week • There should be 10 good GEMs from last year production at SB C.Woody, DC Meeting, 6/13/07

14. Schedule Schedule of GEM shipment to SB: • From last year production we (at WIS) have 16 good fully tested GEMs: 12 standard + 4 Au plated. There should be 10 good GEMs from last year production at SB. • As soon as the total number of good GEMs will reach 24 (number of slots in the shipment box) we will ship the 1st batch to US. This will hopefully happen in ~1 week. This first shipment, should be more than enough to refurbish the west arm. • A second shipment with 24 additional GEMs should be ready for shipment to SB in the second half of July. Refurbishing of the West arm is expected to start at SB within 10d. We shall revisit the overall schedule at our next meeting. C.Woody, DC Meeting, 6/13/07

15. Things are ready at Stony Brook Several CsI GEMs removed from HBD West and rescanned for QE All looked fine (good as new) in QE scan Each showed different response in last flash lamp test in IR ?? • Evaporator working • QE measurement system working • LEGS gas system up and running in recirc mode • with increase flow and safety system • Many new students arriving C.Woody, DC Meeting, 6/13/07

16. Summary • Evaluation of HBD West at Stony Brook is continuing • Need to decide how to install shades to block scintillation light • Reconstruction of HBD West expected to start in about 2 weeks • (~ 2 weeks behind schedule) • Still expect to complete reconstruction by early August and begin • testing • Need to get ready for HBD East arrival at Stony Brook in mid July • It’s going to be a busy summer….. C.Woody, DC Meeting, 6/13/07