Hadron Blind Detector for PHENIX Experiment at RHIC: Construction Update and Pending Design Issues

1. HBD update • NIM paper II: Generic R&D ~ completed • Full scale prototype construction • Pending issues towards final design • Electronics status • Monte Carlo Itzhak Tserruya DC Upgrades meeting, January 14, 2005

2. HBD NIM paper #2: Title: A Hadron Blind Detector for the PHENIX Experiment at RHIC. 1. Introduction 2. HBD Concept 3. Set-up and Experimental conditions 4. Detector response as function of the drift field; 4.1 Detector response to mip and alpha particles 4.2 Detector response to photoelectrons 5. CsI Quantun Efficiency 6. Discharge probability and saturation effec 7. Aging studies 8. Summary and Conclusion Time table - draft under review within the authors - final paper to be posted to phenix-p-l for possible comments within one week. - submit to NIM.

3. Full scale Prototype design Complete set of engineering drawings available at: https://www.phenix.bnl.gov/phenix/WWW/p/draft/ravini/hbd_drawings/prototype

4. Exploded view • This exploded view corresponds to a slightly older design, but the basic concept remains unchanged: • The prototype has a total of 10 panels and not 11 as in this drawing, • The panels on the active area of the detector are glued to the pad plane made of kapton (50μ thick)

5. Prototype status and goals (I) Construction status: • All raw material and components ordered and delivered (Delay on delivery of HV surface mount resistors. Ordered in July 2004. Delivered this week) • All manufactured parts ready (Delay on the delivery of the pad plane. Was shipped from CERN yesterday) • 7 out of 10 panels ready • Assembly jigs in the shops. Expected delivery 1-2 weeks • Mechanical assembly expected to be complete within 4-5 weeks Goals (once the detector box is completed) • Mechanical tolerances • Leak tightness • Flush with N2 while monitoring H2O and O2 • Install large GEM stack • Flush and operate with CF4 • Ship to BNL • Test with prototype electronics

6. Prototype status and goals (II) Large GEMs • The prototype will be equipped with one set of large GEMs (23 x 24 cm2) • 12 large GEMs HV segmented produced at CERN (8 standard + 4 gold plated) • Stretching, mounting and gluing on 5mm wide frame OK • CsI evaporation OK • Tested at 104 gain for more than 2 months. OK • Pending problem: mesh stretching • New set with surface mount HV resistors will be prepared soon.

7. Pending issues towards final design Two main issues: • Acceptance • Detector envelope Other smaller details: • Design new window to allow installation in retracted position starting at r = 25 cm) • Location of gas in/out for window N2 flushing

8. HBD acceptance  acceptance: 4 x 25.5o  acceptance: 6 x 25.5o or even 8x 25.5o

9. Acceptance, number of channels, pad size Central arm acceptance: φ = 90o , |η| = 0.35  θ = ± 19.7o Constraint: (4 connectors)  96 pads per detector element a) Present  acceptance: 4 x 25.5o panel length 260 mm  768 pads per arm Total number of channels: 1536 b) Enlarged  acceptance: 6 x 22.5o panel length 227 mm  1152 pads per arm Total number of channels: 2304 Emerging choice  = 4 x 25.5o  = 6 x 22.5o

10. z 80 cm 120 cm Detector envelope • No problem in r • Very tight in z • z [mm] • Acceptance || < 0.4 535 • Frame width • 2x (5+1) 12 • Detector covers 2x(3/4” +0.5 mm) 39 • (w/o head of screws) • Services 2x40 80 • (prototype has 106 mm) • -------- • 666 Requested HBD envelope: z = 680 mm All external services, HV, LV and signal cables, gas pipes … , will be within this envelope

11. Electronics status Analog electronics (BNL Instrumentation): • Components for 3000 channels ordered. • Few hundred channels will be available soon. • Prototype readout board (for a 10x10 cm2) ready for test. • Provisions are being made for a second prototype board of almost final size to be used with the prototype detector.  Excellent shape Digital electronics (Columbia): • Cables and connectors identified • Prototype FEM under design • Three phases: • Prototype production 5 m • Prototype test 3 m • Final production 6-9 m • Very good progress, but still the limiting factor in the overall schedule: Trying to see whether we can improve it.

12. HBD Monte Carlo • HBD prototype geometry in PISA: • Two arms, 8 detector elements per arm • Acceptance:  = 100o and || = 0.4 in each arm • +/- magnetic field configuration • HBD pattern recognition and tracking – done, as part of the PHENIX reconstruction software in Fun4All framework. • Whole chain works on WIS local PC-farm with pro.56 library using pisaToDST.C with single particle MC, pure HIJING events, HIJING merged with  e+e-

13. Why do we call it HBD? Event display: central HIJING event

14. CB from central HIJING events (b<2fm) 18K events Pattern recognition: • Remove one pad clusters. • Cluster charge > 20 p.e. • Match Central Arms electron tracks to HBD with 3s p-dependent cuts. This matching reduces the number of electrons by a factor of ~3 i.e. the CB by ~10. • Reject “conversions” tracks with amplitude cut (>60 e) • Reject Dalitzes with close hit cut (< 200 mrad) For m > 200 MeV/c2 the rejection factor is > 100

15. Signal and Background Signal:

16. Summary and outlook • Still a lot to do but so far so good. • Getting ready for the final detector construction • Internal proposal for the Collaboration under preparation