Recent DHCAL Developments

José Repond and Lei XiaArgonne National Laboratory

Linear Collider Workshop 2013University of Tokyo

November 11 – 15, 2013

J. Repond - Imaging Calorimeters

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The DHCAL

Description

54 active layers Resistive Plate Chambers with 1 x 1 cm2 pads → ~500,000 readout channels Main stack and tail catcher (TCMT)

Electronic readout

1 – bit (digital) Digitization embedded into calorimeter

Tests at FNAL with Iron absorber in 2010 - 2011

Tests at CERN with Tungsten absorber 2012

1st time in calorimetry

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DHCAL Construction Fall 2008 – Spring 2011

Resistive Plate Chamber

Sprayed 700 glass sheets Over 200 RPCs assembled → Implemented gas and HV connections

Electronic Readout System

10,000 ASICs produced (FNAL) 350 Front-end boards produced

→ glued to pad-boards 35 Data Collectors built

6 Timing and Trigger Modules built

Assembly of Cassettes

54 cassettes assembledEach with 3 RPCs

and 9,216 readout channels

350,208 channel system in first test beam Event displays 10 minutes after closing enclosure

Extensive testing at every step

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Testing in BeamsFermilab MT6

October 2010 – November 2011 1 – 120 GeV Steel absorber (CALICE structure)

CERN PS

May 2012 1 – 10 GeV/c Tungsten absorber (structure provided by CERN)

CERN SPS

June, November 2012 10 – 300 GeV/c Tungsten absorber

Test Beam Muon events Secondary beam

Fermilab 9.4 M 14.3 M

CERN 4.9 M 22.1 M

TOTAL 14.3 M 36.4 M

A unique data sample

RPCs flown to GenevaAll survived transportation

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Recent developments

Improved Resistive Plate Chambers

1-glass design High-rate RPCs

High voltage distribution system

Gas recirculation system

Resistive paint

Resistive paint

Mylar

1.2mm gas gap

Mylar Aluminum foil

1.1mm glass

1.1mm glass

-HV

Signal padsG10 board

Typical RPC design

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1-glass RPCs

Offers many advantages

Pad multiplicity close to one → easier to calibrate Better position resolution → if smaller pads are desired Thinner → t = tchamber + treadout = 2.4 + ~1.5 mm → saves on cost Higher rate capability → roughly a factor of 2

Status

Built several large chambers Tests with cosmic rays very successful → chambers ran for months without problems Both efficiency and pad multiplicity look good

Efficiency Pad multiplicity

J. Repond - The DHCAL

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Rate capability of RPCs

Measurements of efficiency

With 120 GeV protons In Fermilab test beam

Rate limitation

NOT a dead time But a loss of efficiency

Theoretical curves

Excellent description of effect

Rate capability depends

Bulk resistivity Rbulk of resistive plates (Resistivity of resistive coat)

Not a problem for an HCAL at the ILCB.Bilki et al., JINST 4 P06003(2009)

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10-18

10-15

10-12

10-9

10-6

10-3

100

103

106

109

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Poly

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Material

(S

)

C. Pecharromán X. Workshop on RPC and related Detectors (Darmstadt)

Here is the problem

There is a gap between 10-9 and 10-3

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Available resistive plates

108 109 1010 1011 1012 1013102

103

104

105

106

Floatglass

Semi-conductive

glass

Ceramics

Streamer mode

Warm glass

BeijingCBM Requirement

Beijing

INR+CBM

lip Coimbra

ALICE-muon

LHCb

ATLAS

Warsaw

CMS-forward

CMS-barrel

CERN+Bologna

CERN+Rio

Dresden

STAR

ALICE-TOF

Lip+USC

Max

Counting R

ate(

Hz/

cm2)

Volume Resistivity(cm)

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Where to use high-rate RPCs

ILC – Hadron calorimeter (close to beam pipe)

CLIC – Hadron calorimeter (forward direction – 2γ background)

CMS – Hadron calorimeter (forward direction)

Current forward calorimeters inadequate for high-luminosity running

PbWO4 Crystals Scintillator/Brass + Quartz fibers/Steel

To start in year ~2023Luminosity of 5 x 1034 cm-2

(> x10 higher than now)

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High-rate Bakelite RPCsBakelite does not break like glass, is laminated but changes Rbulk depending on humidity but needs to be coated with linseed oil

Gas inlet Gas outlet

Gas flowdirection

Fishing line

Sleeve aroundfishing line

Additional spacer

Use of low Rbulk Bakelite with Rbulk ~ 108 - 1010 and/or Bakelite with resistive layer close to gas gap

Several chambers built at ANL

Gas

Resistive layer for HV

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High-rate Bakelite RPCsBakelite does not break like glass, is laminated but changes Rbulk depending on humidity but needs to be coated with linseed oil

Gas inlet Gas outlet

Gas flowdirection

Fishing line

Sleeve aroundfishing line

Additional spacer

Use of low Rbulk Bakelite with Rbulk ~ 108 - 1010 and/or Bakelite with resistive layer close to gas gap

Several chambers built at ANL

Gas

Resistive layer for HV

Noise measurement: B01

1st run at 6.4 kV Last run, also 6.4kV, RPC rotated 900

Readout area

Fishing lines

(incorporated resistive layers)

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Noise measurementsApplied additional insulationRate 1 – 10 Hz/cm2 (acceptable)Fishing lines clearly visibleSome hot channels (probably on readout board)No hot regions

Cosmic ray testsStack including DHCAL chambers for trackingEfficiency, multiplicity measured as function of HVHigh multiplicity due to Bakelite thickness (2 mm)

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GIF Setup at CERN

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First results from GIF

Source on

Source off

Background rate

Absolute efficiency not yet determined

Clear drop seen with source on

Background rates not corrected for efficiency drop

Irradiation levels still to be determined (calculated)

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Development of semi-conductive glass

Co-operation with COE college (Iowa) and University of Iowa

World leaders in glass studies and development

Vanadium based glass

Resistivity tunable Procedure aimed at industrial manufacture (not expensive)

First samples

Very low resistivity Rbulk ~ 108 Ωcm

New glass plates

Rbulk ~ 1010 Ωcm produced Plates still need to be polished Production still being optimized

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High Voltage Distribution System

Generally

Any large scale imaging calorimeter will need to distribute power in a safe and cost-effective way

HV needs

RPCs need of the order of 6 – 7 kV

Specification of distribution system

Turn on/off individual channels Tune HV value within restricted range (few 100 V) Monitor voltage and current of each channel

Status

Iowa started development First test with RPCs encouraging Work stopped due to lack of funding Size of noise file

(trigger-less acquisition)

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Gas Recycling SystemDHCAL’s preferred gas

Development of ‘Zero Pressure Containment’ System

Work done by University of Iowa/ANL

Status

First parts assembled…

Gas Fraction [%] Global warming potential (100 years, CO2 = 1)

Fraction * GWP

Freon R134a 94.5 1430 1351

Isobutan 5.0 3 0.15

SF6 0.5 22,800 114

Recycling mandatory for larger RPC systems

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Summary

After successful testing of the DHCAL at Fermi and CERN

Further improvements to the active medium and its supplies

Development of 1-glass RPCs (design validated!) Development of low-resistivity bakelite/glass (ongoing, but encouraging) Development of a high-voltage distribution system (stalled) Development of a gas recirculation system (new concept, being assembled)

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Backup

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CMS forward calorimeter

Driven by successful application of PFAs to CMS analysis

Proposal to replace forward calorimeters with an IMAGING CALORIMETER

Several members of CALICE have been contacted by CMS

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Formidable challenge

Charged particle flux

In calorimeter volume up to 50 MHz/cm2 at shower maximum

Total dose

Fluences of 1016 neutrons