Lei Xia Argonne National Laboratory Construction of a Digital Hadron Calorimeter with Resistive Plate Chambers Lei Xia Argonne National Laboratory

RPC DHCAL Collaboration Argonne Burak Bilki Carol Adams Mike Anthony Tim Cundiff Eddie Davis Pat De Lurgio Gary Drake Kurt Francis Robert Furst Vic Guarino Bill Haberichter Andrew Kreps Zeljko Matijas José Repond Jim Schlereth Frank Skrzecz (Jacob Smith) (Daniel Trojand) Dave Underwood Ken Wood Lei Xia Allen Zhao Boston University John Butler Eric Hazen Shouxiang Wu Fermilab Alan Baumbaugh Lou Dal Monte Jim Hoff Scott Holm Ray Yarema IHEP Beijing Qingmin Zhang University of Iowa Burak Bilki Edwin Norbeck David Northacker Yasar Onel McGill University François Corriveau Daniel Trojand UTA Jacob Smith Jaehoon Yu IIT Guang Yang Daniel Kaplan RED = Electronics Contributions GREEN = Mechanical Contributions Yellow = Students BLACK = Physicist RPC 2012

Motivation: physics at the next lepton collider – Physics Benchmarks for the ILC Detectors Required: excellent Jet energy/mass resolution Solution: Particle Flow Algorithm (PFA) RPC 2012

Particle Flow Algorithms Need new approach Particle Flow Algorithms ECAL HCAL γ π+ KL The idea… Charged particles Tracker measured with the Neutral particles Calorimeter Particles in jets Fraction of energy Measured with Resolution [σ2] Charged 65 % Tracker Negligible Photons 25 % ECAL with 15%/√E 0.072 Ejet Neutral Hadrons 10 % ECAL + HCAL with 50%/√E 0.162 Ejet Confusion ≤ 0.242 Ejet 18%/√E Required for 30%/√E Requirements for detector system → Need excellent tracker and high B – field → Large RI of calorimeter → Calorimeter inside coil → Calorimeter as dense as possible (short X0, λI) → Calorimeter with extremely fine segmentation → Single particle energy resolution not critical thin active medium Opens up new possibilities RPC 2012

Digital Hadron Calorimeter (DHCAL) and Choice of active medium Requirement of PFA hadron calorimeter Extremely fine segmentation (~1x1cm2 readout cell)  simple hit counting provide sufficient energy resolution  1bit readout/Digital Hadron Calorimeter (DHCAL) DHCAL  counting charged particles in hadronic showers (instead of measuring dE/dx in the active medium)  the active medium can have poor, or even no dE/dx resolution Thin active medium, embedded readout Cost … What RPC can offer Good position resolution  great for fine segmentation Excellent efficiency for charged particles  great for counting charged particles Large charge fluctuation for single MIP  no dE/dx resolution, poor particle counting on single pad  but this is exactly NOT needed for a DHCAL Can be made very thin Low cost RPC is a perfect choice for a Digital Hadron Calorimeter! RPC 2012

1 m3 – Digital Hadron Calorimeter Physics Prototype Description Readout of 1 x 1 cm2 pads with one threshold (1-bit) → Digital Calorimeter 38 layers in DHCAL and 14 in Tail Catcher, each ~ 1 x 1 m2 Absorber: 18mm Fe + 2mm Cu in DHCAL, thicker Fe plates in Tail Catcher Each layer with 3 RPCs, each 32 x 96 cm2 ~480,000 readout channels Purpose Validate DHCAL concept Gain experience running large RPC systems Measure hadronic showers in great detail Validate hadronic shower models (Geant4) Status Started construction in 2008 Completed in January 2011 Test beam runs started in Oct. 2010 at Fermilab More test beam runs in 2011 Analysis on-going Critical for PFA validation RPC 2012 6 6 6

RPC Construction RPC design RPC production Resistive paint spraying Glass Pad board Frame RPC design 2 – glass RPCs (chosen for construction) 1 – glass RPCs (developed at Argonne) Gas gap size 1.1mm Well arranged gas flow (by fishing line + sleeve spacer) Total RPC thickness < 3.4mm Dead area ~5% (frame ~3%, spacer ~2%) RPC production ~114 for DHCAL + 42 for TCMT + spares  at the end, produced ~ 205 RPC’s Resistive paint spraying Uses two-component artist paint Built dedicated spraying booth Accept plates with value 1 – 5 MΩ/□ Achieved a yield of ~60% overall Gap assembly Developed precision cutting/gluing fixtures Production rate 1RPC/day/tech RPC 2012 7 7 7

Quality Assurance Pressure tests Gap size measurement HV tests All RPC’s are tested with 0.3 inch of water pressure Gap size measurement Thickness of 1st batch RPC’s measured along the edges (Gap size away from the edges is assured by spacers) Gap sizes along edges vary within 0.1 mm Corners typically thicker (up to 0.3mm, but limited effect) HV tests ALL RPC’s tested up to 7.0 kV before placing readout board on top (nominal operating voltage is 6.3 kV) Cosmic ray test 9 of the 1st batch RPC’s were tested on a cosmic ray test stand for performance (efficiency, multiplicity, uniformity) All other RPC’s were later tested in vertical position with cosmic rays, after assembled into cassettes Overall yield: ~95% RPC 2012 8 8

Design consideration for readout system System is built around a custom ASIC (DCAL chip) Designed to handle huge number of channels + low channel density (1cm2 pad, 1m2 planes, 38+14 planes  480K channels) 64ch, handling 8x8 RPC active area System tailored for test beam / prototype tests, NOT for real colliding beam detector Facilitates all possible tests (test beam, cosmic ray test, noise runs, system diagnostics, etc) Avoided cutting-edge technology and fancy functionality Didn’t optimize for minimum power consumption, minimum data links, minimum thickness, etc. Compromises aimed at proving detector concept  key in getting system up quickly and running reliably Two basic running mode External triggering mode  primary method for beam events, also used for cosmic ray test 20-stage pipeline  2μs latency @ 100ns clock cycle Deadtimeless readout (within rate limit) Self triggering mode primary method for noise runs, also used for cosmic ray, beam runs Powerful running mode for monitoring RPC condition Equally powerful for cosmic ray running and some beam running as well RPC 2012

Readout system overview VME Interface Data Collectors – Need 10 Timing Module Double Width - 16 Outputs Ext. Trig In master IN 6U VME Crate To PC Data Concentrator Front End Board with DCAL Chips & Integrated DCON Chambers – 3 per plane Data Collectors – Need 10 VME Interface master IN Ext. Trig In To PC Timing Module Double Width - 16 Outputs Communication Link - 1 per Front-End Bd 6U VME Crate Square Meter Plane RPC 2012 10

The DCAL Chip Developed by Input Threshold Readout Versions FNAL and Argonne Input 64 channels High gain (GEMs, micromegas…) with minimum threshold ~ 5 fC Low gain (RPCs) with minimum thrshold ~ 30 fC Threshold Set by 8 – bit DAC (up to ~600 fC) Common to 64 channels Readout Triggerless (noise measurements) Triggered (cosmic, test beam) Versions DCAL I: initial round (analog circuitry not optimized) DCAL II: some minor problems (used in vertical slice test) DCAL III: no identified problems (final production: used in current test beam) Production of DCAL III 11 wafers, 10,300 chips, fabricated, packaged, tested Hits/100 tries Threshold (DAC counts) RPC 2012 Threshold (DAC counts) 11 11 11

FrontEnd/DCON board + Pad board Resistive paint Mylar 1.2mm gas gap Aluminum foil 0.85mm glass 1.1mm glass Signal pads HV ASIC Front-End PCB Pad Board Conductive Epoxy Glue Communication Link 8.6 mm Fishing line spacers Build FE and pad boards separately to avoid blind and buried vias (cost and feasibility issue) Each board contains 1536 channels and 24 ASICs The data concentrator is implemented into the same board Glue the two boards together with conductive epoxy FE board need to pass computer test before gluing Extensive tests (S-curves, noise rates…) 3 – 6 hours/board Accepted boards with less than 4/1536 dead channels RPC 2012 12

Timing and Trigger Module (TTM) Data Collector DCOL Power supply systems Low voltage system High voltage system Back end electronics Timing and Trigger Module (TTM) Data Collector DCOL Gas System RPC 2012 13

Cassette Assembly Assembly Cassette Testing - FEB’s are placed onto RPC’s directly (no gluing), positioning and contact is assured by pressure asserted from cassette - Cassette is compressed horizontally with a set of 4 (Badminton) strings - Strings are tensioned to ~20 lbs each, very few broken strings Cassette Testing - Cassettes were tested with CR before shipping to test beam 38+14 cassettes assembled RPC 2012 14

Digital calorimeter: will it work? During the time we were busy with the DHCAL construction (2010), Richard Wigmans, who wrote a well-known book on calorimeter, claimed at a calorimeter conference: “ ‘Digital’ calorimetry was tried and abandoned for good reason (1983) ” Unfortunately, this was said too late – we were very close to finishing the DHCAL construction Even more unfortunately, it only took us a short while in the test beam to prove him wrong! RPC 2012

The DHCAL in the Test Beam Fermilab test beam run dates DHCAL layers RPC_TCMT layers SC_TCMT layers Total RPC layers Total layers Readout channels 10/14/2010 – 11/3/2010 38 16 54 350,208+320 1/7/2011 – 1/10/2011 8 46 350,208+160 1/11/2011 – 1/20/2011 4 42 50 387,072+160 1/21/2011 – 2/4/2011 9 6 47 53 433,152+120 2/5/2011 – 2/7/2011 13 51 470,016+0 4/6/2011 – 5/11/2011 14 52 479,232+0 5/26/2011 – 6/28/2011 11/2/2011 – 12/6/2011 460800 Run I Run II Run III Run IV Run V More test beam in 2012, at CERN ~ 480K readout channels ~ 35M events RPC 2012 DHCAL Tail Catcher (TCMT)

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First beam: muons One muon Three muons Four muons A lot of muons RPC 2012 18

Next: pions 60 GeV pions measured in DHCal RPC 2012 19

And also positrons 32 GeV 25 GeV 20 GeV 16 GeV RPC 2012 12 GeV 20

And occasionally, neutral hadron RPC 2012 21

Summary The construction of the DHCAL prototype (+Tail Catcher) is complete Test beam at Fermilab started in October 2010 Had 5 successful test beam campaigns in 2010/11 DHCAL prototype (+Tail Catcher) works extremely well A lot of good data collected, analysis is on-going First look at data is very encouraging! More test beam/more data is on the way 2012 : At CERN with Tungsten absorber For more details of the DHCAL performance and preliminary physics results Please see: Next talk, by Jose Repond (Analysis of DHCAL Events) Poster, by B. Bilki (Response of the DHCAL to Hadrons and Positrons) RPC 2012 22