Towards an RPC-based HCAL DesignTowards an RPC-based HCAL Design

Stephen R. Magill Stephen R. Magill

Argonne National LaboratoryArgonne National Laboratory

Digital HCAL for an E-Flow Calorimeter

Use of RPCs for DHCAL

RPC Design Choices, Issues

Readout Electronics

Time Scales

Summary of Recent Mini-Workshop Summary of Recent Mini-Workshop on RPCs for a LC HCALon RPCs for a LC HCAL

Participants :

G. Drake, V. Guarino, S. Kuhlmann, S. Magill, B. Musgrave, J. Repond, D.

Underwood,B. Wicklund

Argonne National Laboratory

J. Butler, M. Narain Boston University

E. Blucher, M. OregliaUniversity of Chicago

Topics :

RPC Parameters

Design Choices/Optimizations

Issues/Concerns for R&D

Mechanical/Electronics

R&D Time Scales

Organized by J. Repond at ANL – November 1

Digital HCAL for an E-Flow CalorimeterDigital HCAL for an E-Flow Calorimeter

Charged particles~ 62% of jet energy

-> Tracker /pT ~ 5 X 10-5 pT

190 MeV energy resolution to 100 GeV Jet

Photons ~ 25% of jet energy

-> ECAL /E ~ 15-20%/E : ~900 MeV to energy resolution

Neutral Hadrons ~ 13% of jet energy

-> HCAL <3 GeV to resolution -> /E < 80%/E

W, Z

30%/M

75%/M

Can explore EWSB thru the interactions : e+e- -> WW and e+e- -> ZZ

-> Requires Z,W ID from dijets-> Can’t use (traditional) constrained fits

Compare to digital

KKLL00 Analysis – Analysis –

Analog Readout Analog Readout

/mean ~ 26%

Eaverage ~ 13 GeV

Average : ~43 MeV/hit

Analog EM + Digital HAD x calibration

Slope = 23 hits/GeV

KKLL00 Analysis - Analysis -

Digital Readout Digital Readout

/mean ~ 24%

Digital Analog

Generic designHV

Gas

Pick-up pad(s)

Graphite

MylarResistive Plates: Glass or Bakelite

Advantages: Thin layer (≤ 10 mm) High single particle efficiencies (> 95%) Flexible geometrical design Flexible pad readout segmentation Printed circuit Simple Front-End readout Reliable Underlying physics mostly understood see http://www.coimbra.lip.pt/~rpc2001/talks.html Cheap

Use of RPCs for Digital HCALUse of RPCs for Digital HCAL

Resistive plates

Glass cheap, simple

Bakelite needs to be coated with linseed oil source of major problem with BaBar chambers

Geometry

Glass thickness Several thicknesses on hand

Gas gap thickness Smaller → reduced HV

Multiple gaps Smaller gaps → improved long-term stability Higher efficiency

Completely different design

Preferred

HARP Experiment at CERN: TOF

Preferred

Particle

Design ChoicesDesign Choices

Operation

Avalanche mode

Faster (~10kHz) Lower HV Smaller signal (~1pC) Needs pre-amplifier Better long-term prognosis No multiple streamers

Streamer mode Slower (~1kHz) Higher HV Large signals (~100pC) Sharp signal Multiple streamers

Cosmic ray tests at ANL

Charge [pC]

Charge [pC]

High Voltage [kV]

Preferred

Gas Mixture

Freon/Argon/IsoButane 62:30:8

Used by Belle (does not suppress streamers)

Freon/IsoButane/SulfurHexafluoride 90:5:5 Used by HARP (suppresses streamers)

Many more…

Safety with HV

Using up to 10kV Can be reduced with smaller gaps by operation in avalanche mode

Cross talk between pads

Significant charge on neighboring pad Reduced with higher resistivity graphite layer 40kΩ/□ → 200kΩ/□ → 1MΩ/ٱ pad – ground plane distance dependence Signal shape very different Easy to discriminate: cross talk at 1- 4% level

Long term operation

Significant experience elsewhere (L3) Reason for choosing avalanche mode/multiple gaps

Overall Thickness

Most likely will need 10 mm

Calibration

Will be needed?

Pad structureIssues and ConcernsIssues and Concerns

Assume LLC = 0.5x1034 cm-2s-1 = 0.5x10-2 pb-1s-1

σ1γ (500 GeV) = 4 pb → N/s = 0.02

σ2γ→ee(800 GeV) = 34 mb → N/s = 170x106

σ2γ→μμ(800 GeV) = 473 nb → N/s = 2400

σ2γ→h(800 GeV) = 189 nb → N/s = 945

From V M Budnev et al.Phys. Lett. 15(1974) 181-282

Easy

Not our problem

Should be ok

Recharging time of RPCs :

Avalanche mode ~104 Hz Streamer mode ~103 Hz

Rate EstimationsRate Estimations

Particle rates from PYTHIA

Beam pipe 24.1 % <E> = 15.7 GeV

Endcaps 75.8 % <E> = 1.53 GeV

Rate/endcap = 613 Hz 283 Hz (E> 1GeV)

Barrel 0.06 % <E> = 5.0 GeV

A Readout Electronics System for A Readout Electronics System for RPCsRPCs

General Concepts

Each Channel has a Discriminator

– a 1-Bit ADC

Timestamp Each Hit

Store Timestamps in Local Buffers,

Read Out Periodically

No Trigger System

Read Out Timestamps into Trigger Processor

Use Timestamps to Construct Hits

Works Well for Low Event Rates and Low Noise Rates

Like MINOS DAQ

Custom Front-End Custom Front-End ICIC

Essential Functions :

Low-Noise Preamp (Needed for Avalanche Mode)

Discriminator

Timestamp Circuitry

Holding Buffer

ReadoutFor Testbeam (~400K Channels) –

Will Probably Need Dedicated Run (~$100K, 3-6 Months, Packaging, Wafer Testing...)

Like CDF SVX Detector!

For Production (~50M Channels) –

Cost of Custom IC Design & Fab Will Be Worth It

<< $1 /Channel for Chip

Front-End PCB Front-End PCB DesignDesign

Top View – highly-integratedapproach

Cross-sectional view ofmulti-layer PCB

Back-End ReadoutBack-End Readout Essential Functions :

Receive Serial Data Streams

from Front Ends

Concentrate Data

Form "Time Frames“

(~1 Sec for MINOS)

Send Data to Trigger Processor

Realization :

Use VME Crates for Infrastructure

Data Concentrators Receive Serial data streams from Front Ends

Data Concentrators Also Provide Clock & Control

Until September of 2004

Finalize prototype design

Construct 40 layers of 1m2 corresponding to an 1 m3 HCAL section

Build gas mixing/distribution system

Select/purchase HV/LV power supplies

Next 6 months

Build chambers: explore different designs

R&D with resistive layer

Initiate design of prototype chambers

Design and build readout pads (multilayer boards)

Design and build readout system for O(100 channels)

Design custom readout chip

Prototype

R&D

Evaluate various designs with respect to :

Efficiency Noise rate Rate capability? Cross-talk

Evaluate in CERN test beam :

Viability of designValidation of MC Comparison with analog HCAL

Time ScalesTime Scales