Readout Board Designfor Gas Electron Multiplier Detectors

for Use in a Proposed Upgradeof the CMS Hadron Calorimeter

Elizabeth StarlingMarcus Hohlmann

Kimberley Walton, Aiwu Zhang[March 7th, 2014]

Introduction

Each layer of the CMS detector is designed to stop/measure a different kind of particle. The hadron calorimeter (HCAL) is

one of these layers.

1)Hadrons enter HCAL2)They interact with the brass absorber material and create showers3)The energy of the shower, which we can measure, is proportional to the energy of the particle!

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The Problem

However, HCAL has its limits.

Can: measure the scintillation energy of the particles,

Cannot: measure their position or movement within the detector.

If we want more data, we need to upgrade the calorimeter such that it can see particle flow as well as energies – from a hadron calorimeter (HCAL) to a

particle flow calorimeter (PFCAL).

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The Solution!

Unlike HCAL’s current design, GEM detectors can easily detect the location of particle hits – we’ve used this fact to our advantage for our

muon tomography station.

We need to design a readout board that will be capable of accurately measuring the location of

each particle hit on the GEM detector.

The solution: a segmented pad readout board!

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Design – Basics

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Hadron showers are large! They can be several centimeters across, so the pads can be wider than the strips from previous readout boards!

Detectors will be “sandwiched” in-between brass absorber

plates – these plates cause the showers that the GEM

detectors can then pick up.

Design – Square Pads

10 cm x 10 cm active area

11 rows of 11 square pads: 121 total.

Each pad is:8.975 mm x 8.975 mm

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Design – Square Pads

All read-out components are routed to a single APV:•2 ground connections (top left, bottom right)

•121 pad connections•5 auxiliary connectors – to allow for easier “plug-and-play”

access when testing the boardsMarch 7th, 2014 Florida Academy of Sciences 7

Panasonic footprint

Design – Square Pads

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All pads are routed underneath each other

on a mid-layer.

Does cross-talk make a measureable difference?

To find out, we routed three rows all the way

across!

Design – Chevrons

10 cm x 10 cm active area

“Zig-zag”-style chevrons!

Chevron pads give us different information than the square pads, and improves upon the

shower descriptions.

Because of the different horizontal segmentation, the

charge sharing between adjacent pads can tell us more about the

particles and their positions!March 7th, 2014 Florida Academy of Sciences 9

Design – Chevrons

In order to maintain the square shape of the active area and keep to a single Panasonic connector,

we used three types of pads:

•110 full-chevron pads – formed by cutting the square pads diagonally in half and flipping one half.•12 half-chevron pads to “fill in” the main square!•5 merged half-chevron pads, to fit to a single APV

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What’s Next

• Have the boards produced by outside industry• Test the boards:– Do they accomplish our goals?– What differences do we see between the square

and chevron pads?

• Make a square “pixel” style board, with 9 square pixels for every 1 square pad.– Is this possible at the 10x10 scale? Routing?

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What’s Next

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121 square pads 1,089 square pixels

References

Image on slides #2, 5: http://en.wikipedia.org/wiki/Compact_Muon_Solenoid

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