PHENIX RPC RD EFFORT Beau Meredith University of

PHENIX RPC R&D EFFORT Beau Meredith (University of Illinois at Urbana-Champaign) for the PHENIX Collaboration IX International Workshop on RPCs and Related Detectors Mumbai, India 1

RPC Technology in PHENIX RPC R&D This talk PHENIX specific R&D GSU UIUC CU Boulder RPC Gap Production See Byungsik Hong’s talk Gap production at Korea University, Physics Motivation RPC Assembly & QA Rusty Towell’s Talk Integration into PHENIX, HPL testing RPC FACTORY AT BNL 2

Outline n Introduction n PHENIX experiment Physics Motivation RPC forward upgrade for muon spectrometer n Bakelite RPC R&D at PHENIX institutions n n n Gap construction Using gaps to test PHENIX specific parameters Basic R&D results 3

RHIC/PHENIX BRAHMS PHOBOS PHENIX RHIC, lenght: 3. 83 km STAR n Two Muon Spectrometers, 1. 2<|h| 2. 4, Δφ=2π n n n Tracking: Wire chambers with cathode strip readout, 3 stations/arm with multiple views (Mu. Tr) Identification: Iarocci streamer tubes, 5 detection planes (Mu. ID) Lampshade magnets produce radial magnetic field n Can obtain momentum from change in azimuthal angle Δφ 4

Motivation for RPC Forward Upgrade quark spin orbital angular momentum gluon spin Experiment n √s = 500 Ge. V polarized pp collisions n Probe the quark and anti-quark spin contributions via high momentum muons from the W bosons n Need to at least increase rejection factor of muon arms from ~500 to 6, 000 n Introduce RPC forward upgrade n We aim to have a rejection factor of ~ 10, 000 For more details see Byungsik Hong’s Talk 5

PHENIX Muon Trigger Upgrade RPC 1: 32 RPC detector modules (768 read-out channels) RPC 2: 128 RPC detector modules (15392 read-out channels) RPC 3: 96 RPC detector modules (11488 read-out channels) RPC 3 n n RPC 23 RPC 1 (a, b) Baseline trigger Consists of n RPC 1 or Mu. Tr 1 n Mu. Tr 2 (wire chamber with cathode strip readout) n RPC 2 n RPC 3 Trigger makes momentum cut on muons n Draw line between RPC 1, 2 hit positions n Project this line onto Mu. Tr 2 n Require hit position in Mu. Tr 2 to be within 3 strips of projection RPC 2 RPC 3 Strip Layout for RPCs, Mu. Tr CSC (Mu. Tr 2) 6

PHENIX Bakelite RPC R&D n Start from the CMS endcap design n Use Italian bakelite n Purpose of R&D is n n to acquire experience and 1 st hand knowledge of technology in group to carry out R&D on PHENIX specific performance parameters PHENIX RPC Detector Requirements Efficiency 95% Time resolution 3 ns Average cluster size 2 strips Rate capability 0. 5 k. Hz/cm 2 Best Position Resolution 1 cm Number of streamers 10 % 2 mm gas gaps Gas mixture: 95% R 134 a, 4. 5% Isobutane, 0. 5% SF 6 7

Four RPC Test Stands n PHENIX has test stands at four different institutions. Each test stand is focused on different aspects of RPC R&D. GSU UIUC CU BNL n Georgia State University (GSU) – built and tested 5 generations of prototypes n University of Colorado at Boulder (CU) – conducted performance tests and integration studies for FEE and RPC detectors n University of Illinois at Urbana-Champaign (UIUC) – performed position resolution studies for small strip sizes, SF 6 scan, non-uniform gap study n Brookhaven National Laboratory (BNL) – will carry out QA of prototypes and fully assembled detector modules 8

GSU Prototype Generations 3 rd generation Generation Number of RPCs Sizes Notes 1 st 2 46 cmx 46 cm 2 mm gaps Initial effort 2 nd 2 23 cmx 23 cm 2, 2. 4 mm gaps Signal study 8 30 cmx 30 cm, 23 x 23 cm 1. 6, 2. 0 mm gaps Gaps sent to CU for study 6 30 cmx 30 cm 60 cmx 60 cm 2 mm gaps Added Cu wrap, high rb epoxy for edges 4 30 cmx 30 cm 2 glass, 2 bakelite 2 mm gaps Add edge spacers protruding beyond bakelite edge, EVA glue 3 rd 4 th 5 th Gap Production 3 rd generation Double Gap Assembly 9

Example – GSU Design (Generation 3) n GSU gaps built for FEE tests at CU with different size strips n Use PCB sandwiched between two single gaps n Shown PCB consists of 5 x 4 cm x 20 cm strips and 11 x 0. 5 cm x 20 cm strips; optional termination 10

Studying the CMS Design n Wrap top and bottom copper sheet together TDC spectrum before wrap n n n Use polycarbonate spacers that protrude beyond the bakelite edges Use EVA glue to keep the dark currents low After Use oiled gaps to keep noise rate low 11

Clustering Algorithm at Level 1? n Is a cluster algorithm needed in the level 1 trigger? n n Full GEANT simulation of trigger performance confirms that the use of raw hit info leads to sufficiently high trigger rejection n No need for clustering algorithm A prototype was tested by CU with 0. 5 cm strips n The setup, cluster size, and efficiency curves are shown on the next slide n Generation 3 GSU gaps were used in the testing 12

CU Setup and Results Paddle Scintillator Finger Scintillators RPC Notes: n Cluster Size 0. 5 cm strips used Efficiency n Additional shower rejection paddle not shown Use scope to view and analyze output pulses Fit cluster size data by assuming a hitinducing Gaussian radius. Input resulting distribution into trigger HV (k. V) simulation 13

Trigger Simulation Results n 997, 710 pythia √s = 500 Ge. V pp events run through GEANT n Rejection factors are combined for both muon arms Azimuthal angle cut between RPC 1, 2 Trigger Efficiency Ge. V muons) (25 Rejection Factor 2 degree cut 95% N / 92% S 15, 600 3 degree cut 98% N / 96% S 9, 317 This meets our criteria of R >10, 000 14

CU Timing Resolution Study n We need timing resolution of < 3 ns Remove beam related and cosmic muon backgrounds n Use CMS amplifier/discriminator board n Will not terminating the strips affect the timing resolution, efficiency? n End Center 35. 5 cm RPC n Ω CMS amplifier discriminator (3. 6 ns) Measure timing resolution and efficiency at two locations on strip with and without termination CMS FEE DAQ Hit position Center with Termination End without Termination FEE Efficiency (%) 98. 6 96. 1 99. 6 Time resolution (ns) 1. 34 1. 32 1. 49 15

UIUC R&D Setup n Position Resolution Studies n Non-uniform gap tests n SF 6 Scan Drift Chambers (resolution ~ 1 mm) Timing Scintillators Allows precise position measurements in x and y directions 2 mm teflon spacers RPCs Signal Plane n n 2 mm thick Bakelite Graphite Prototypes are small, open gap designs which can be easily modified Flow gas through cylinders to immerse open gap RPCs 16

RPC Position Resolution n Use three methods to calculate position of muons incident on a RPC n Cluster Center Method n Strip with maximum charge – ADC Max Method n Mean of Gaussian fit to charge distribution on strips – Gaussian Method n Compare position to drift chamber position to calculate position resolution 17

Example Position Resolution Plots Cluster Center 0. 3 cm strips s = 0. 26 cm ADC Max s = 0. 30 cm Gaussian s = 0. 22 cm 1. 0 cm strips s = 0. 46 cm s = 0. 64 cm s = 0. 45 cm 18

Gaussian Position Resolution vs Strip Width Bad Fit 1. 0 cm strips 0. 6 cm strips 0. 3 cm strips 1. 0 cm 0. 3 cm 0. 6 cm 19

Performance Study: non-uniform Gap Original uniform double gap design 19 cm 2 mm Top Gap 2 mm Readout Strips 17 cm Bottom Gap 6 cm 1 cm 0. 2 cm strip separation Strip # 1 20

Performance Study: non-uniform Gap Non-uniform double gap design 19 cm Top Gap 2. 2 mm Readout Strips 17 cm Bottom Gap 6 cm Strip # 1 21

2 D Efficiency 9. 3 k. V Tracking Problem on left hand side for this set of data Top Gap 2 mm 22

2 D Efficiency 9. 5 k. V 2 mm 23

2 D Efficiency 9. 7 k. V 2 mm 24

2 D Efficiency 9. 9 k. V 2 mm 25

2 D Efficiency 10. 1 k. V 2 mm 26

2 D Efficiency 10. 3 k. V 2 mm 27

RPC used for recent SF 6 Scan Polycarbonate (only on sides) 19 cm 2. 09 mm 17 cm Strip # 15 6 cm 1 cm 0. 2 cm strip separation 28

SF 6 Scan Note: Gap Size = 2. 09 mm 1. 0 cm strips SF 6 = 0. 1% 95% SF 6 = 0. 25% SF 6 = 0. 5% SF 6 = 1. 0% 50% 29

Rate Capability Study 6 cm cylindrical 0. 6 milli. Ci Fe 55 sources placed between gas gaps 19 cm 2. 09 mm 17 cm 6 cm 1 cm 0. 2 cm strip separation 30

Rate Capability Study ~ 0. 05 k. Hz ~ 0. 5 k. Hz ~ 9 k. Hz Source 31

Concluding Remarks n We use the CMS endcap RPC technology in the PHENIX forward trigger upgrade n PHENIX institutions have been involved in n Building prototype gaps n Testing PHENIX specific parameters n Performing basic R&D 32

Position Resolution 0. 3 cm strips Cluster Center ADC Max Gauss 1. 0 cm strips Cluster Center 0. 6 cm strips Position Resolution (cm) Cluster Center ADC Max Gauss HV (-kv) 33