RPC Update José Repond Argonne National Laboratory American Working Group On Linear Collider Calorimetry 16 September 2003 What’s new since Cornell…

New chamber construction Tests of geometrical acceptance Multi-channel VME boards Simulation studies Plans for the next few months Outline

Argonne built 3 chambers early in extensive tests with single pads - extensive tests with multi-pads - geometrical tests (→ see later) Boston University (John Butler and Meenakshi Narain) - initiated construction of additional chambers - first iteration on channel construction - all other parts on hand - cosmic ray test stand is set-up; gas is ordered - comparison of multi-gap chambers with single gap chambers - tests with different gas mixtures - construction of larger chambers (33 x 100 cm 2 ) Chamber construction

Geometrical Acceptance Cosmic ray test stand at University of Chicago Trigger Counters RPC Drift Chamber x z y Drift Chamber track with 250 μm resolution Running in streamer mode… Abigail Kaboth,Ed Blucher, Mark Oreglia and Sasha Glazov

Efficiency across the spacer direction 1.1 mm 0.64 mm Spacers (5 cm apart) HV = 7.4 kV HV = 7.6 kV Half width about 1.8 mm Є ~ 15% x 3 mm = 45% mm = 100% x 0.45 mm Select vertical tracks only Half width is about 1.1 mm scan Spacer Ø is 0.64 mm

Efficiency across and along the spacer direction High Voltage lead Across Along HV = 7.4 kV HV = 7.6 kV HV = 7.4 kV Efficiency drops away from HV lead Effect reduced with higher HV setting Effect not observed along spacer Effect (across) corresponds to Δ=100 V/6 cm Still to be investigated in more detail

Multi-channel VME readout Gary Drake (ANL) and Charlie Nelson (FNAL) 6U x 160 VME board VME64 compliant Contains 64 discriminators Optional amplification Records time-stamps of hits and hit patterns

64 channels of discriminator Built as 2 – channel SIPs Fully differential input Amplifier can be jumped across Common threshold voltage (using on – board DAC) When one (or more) discriminators fire Latch value of timestamp counter Record state of all 64 channels Resulting data words written to readout buffer

Timestamp counter Runs at 10 MHz → 100 ns resolution Reset once per second from timing module in crate Status SIPs Design complete Layout complete Fabrication complete Assembly complete being tested VME boards Design complete Layout complete Fabricated 4 boards Assembly completed being tested Software Using V X works Collaboration with NuMI Off-axis Potential hang-up Alternative based on PCI – VMEbus adapter being investigated

Conclusions presented at Cornell EM and HAD showers appear narrower in a DHCAL with RPCs compared to a DHCAL with Scintillator This effect is due to larger and wider cloud of deposits from electrons (and protons in HAD showers) in Scintillator compared to RPCs The results were obtained with a threshold for hits E 0 at 0 With increasing E 0 in Scintillator Radius and E resolution of EM showers decreases Radius of HAD shower remains large (due to protons) Simulation of 1 m 3 Prototype Lei Xia (ANL)

Digital readout – Pad size and linearity Electron energy (GeV) Total number of hits Definition: Linearity 1.Fit the detector response with a simple function: N(hits) = P1 x E(shower) P2 P1 and P2 are fitting parameters. This simple function works amazingly well. 2. P2 = 1 means perfect linearity Pad size = 40x40mm RPC as active media 2

Pad size and linearity: Electron Number of hits increases as pad size gets smaller Energy resolution gets better Detector linearity gets better Very good for pad sizes around 0.2 x 0.2 mm 2

Pad size and linearity: Pion – surprise! Detector has linear response only for pad sizes around 5 x 5 mm 2 For smaller pad sizes: response over – linear! Degrades energy resolution Why?

Pad size and linearity: Cross-talk? -- No! Change of gas gap thickness from 1.2 mm to 0.1 mm Reduces cross-talk Non-linearity remains the same

Plans for the next few months Application of graphite layer Workable paint in hand Explore silk screening Construction of chambers Build single – gap chambers Design larger chambers Geometrical efficiencies Investigate effect of HV leads and spacers Gas Investigate different mixtures Multi-channel VME readout Debug, program, use…