SHMS GEM Tracker - Jefferson Lab · 3 12 GeV Upgrade Hall C Coll. Meeting 2/21/2014 SHMS HMS In...

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SHMS GEM Tracker Status Update

×  Overview

×  Test results

×  Summary

Hall C Coll. Meeting 2/21/2014

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12 GeV Upgrade


SHMS

HMS

In order to reach forward scattering angles of 5.5◦ and to increase the solid angle of the spectrometer, a 3◦ horizontal bend superconducting dipole magnet will be placed in front of the first quadrupole, at ~1◦ to the beam-line.

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�e SHMS Magnet

Dipole 18.4 Degree Bend Max Field: 4.76 T EFL: 2.85 m

Q2 Q3 Max Gradient: 14.4 T/m EFL: 1.61 m

Q1 Max Gradient: 10.63 T/m EFL: 1.86m

Bender 3 Degree Bend Max Field: 3.11 T EFL: 0.75 m

Collimator/Sieve

GEM Tracker

Ø  An active collimation system is needed for the SHMS. Ø  A pair of interchangeable collimator and sieve slit will be permanently attached in

front of the first quadrupole magnet. Ø  In addition to the fixed collimators a GEM tracker will be added (can be inserted in

front of the horizontal bender). The GEM tracker is for optics calibration only, hence will be used for very low beam current (~10nA). The tracker defines the initial position of the particle trajectory entering the horizontal bend magnet and acts as an active sieve slit. The tracker and the sieve slit in front of the quadrupole magnet can be used to map out the transport properties of the entire SHMS within the geometrical acceptance defined by the fixed collimator.


Gas Electron Multiplier (GEM)

Thin, metal-coated polymer foil is chemically pierced with a high density of holes. When applying a voltage difference, each hole acts as an individual proportional counter, and electrons released on the top side drift into the hole, multiply in avalanche, and get transferred to the other side.

Typical geometry:   5 µm Cu on 50 µm Kapton   70 µm holes at 140 µm pitch   50 - 100 Independent Proportional counters/cm2

F. Sauli, Nucl. Instrum. Methods A386(1997)531

70µm 140µm

50 µm Kapton +5 µm Cu both sides Kapton 50 µm Copper 5 µm

U.V.

Photo-resist Mask

70 µm

50 µm

Double-mask photolitographic process

Metal etching by chemical solution

Kapton etching using Cu as mask

Low field (200 V/cm)

High field (2.5 kV/cm)

GEM Foils Construction

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S. Bachmann et al, Charge amplification and transfer processes in the gas electron multiplier Nucl. Instr. and Meth. A438(1999)376


GEM Detectors Principle

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Ø  Charged particles ionize gas in the drift

volume

Ø  Primary electrons drift to the GEM holes

following the E-filed lines

Ø  Electron multiplication due to the strong

E-field in the holes

Ø  Use of two to three layers in cascade

results in high gain (up to 105 in triple

GEM)

Ø  Readout board collects charge


GEM Readout

Electrons are collected on patterned readout boards. A fast signal can be detected on the lower GEM electrode for triggering or energy discrimination. All readout electrodes are at ground potential.

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Two orthogonal sets of parallel strips at 400µm pitch engraved on 50µm Kapton 80µm wide on upper side, 340µm wide on lower side (for equal charge sharing)

A. Bressan et al, Nucl. Instr. and Meth. A425(1999)254


SHMS GEM Tracker

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Readout PCB

Drift Detector Base

GEM foils

Ø  3 GEM foils : 160mm x 160mm

(153.6mm x 153.6mm active area)

Ø  External dimension: 240mm 240mm x 16mm

Ø  Drift board

Ø  Readout board 400µm pitch X and Y

Ø  Panasonic connectors (128 pins per axis)

GEM tracker is a self-stretched triple GEM


GEM Test

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Single channel test All channels connected to APV card

APV cards (Analog Pipeline Voltage )

Ø  Scalable Readout System (SRS)

developed by RD51 Collaboration (CERN)

Ø  APV25 cards, ADC board, FEC card

Ø  Data transferred through Gb Ethernet

Ø  ALICE DAQ (DATE & AMORE)

GEM Readout System & DAQ

SRS ALICE DAQ


FEC

ADC

GEM Test


APV25 raw data ADC analog signal

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Gas Mixture Ar/CO2 (70/30)


Cosmic Test Results

Y-strips X-strips

Cluster: X-strips

charge distribution and cluster size distribution in X and Y strips

Cluster :Y-strips


y-strips (340 mm)

x-strips (80 mm)

2-D Readout Strips

=

=

=

=

=

=

GEM + APV Readout Map


=

=

=

=

=

=

Front-end pad Back-end pad


Correlation of Cluster Amplitudes

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X/Y strips charge sharing Correct map & high stat.

Charge sharing (correct map)

Charge sharing (incorrect map)


2-D Hit Map from Cosmic Data


Gap for separation of electrodes

Testing GEM Foils Ø  Quality control (visual inspection)

Ø  Understand sectoring and HV routing (notice small resistors called “surface mounts”)

Ø  Place each foil in a sealed nitrogen- filled box and measure leakage current (~0.3 nA @ 400V)

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GEM & Shield Holder Lead shielding & box Boron-poly shielding Lead shielding & box

Rail (tracker can slide and retracted)

Summary


Accomplished Ø  Have correct mapping for both GEMs.

Ø  SRS is set up with ALICE DAQ and working properly.

Ø  GEM tracker test was successful and is ready.

Ø  All foils for second GEM (spare) were tested and are good.

In progress

Ø  Assembly of the GEM holder.

Ø  Completing GEM tracker technical notes (located at my JLab webpage)*

Ø  Assembly of the second GEM.

Ø  Test of spare GEM.

Ø  Integrating DATE into CODA

* https://userweb.jlab.org/~mitras/TechNotes.html

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Acknowledgement


² MEP group at MSU (D. Dutta)

² Colleagues at JLab (M. Jones, B. Sawatzky, S. Furches)

² UVA detector lab (K. Gnanvo, V. Nelyubin)

²  Colleagues at CERN and FIT

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SHMS GEM Tracker - Jefferson Lab · 3 12 GeV Upgrade Hall C Coll. Meeting 2/21/2014 SHMS HMS In...

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