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Cost Reduction for Gas Electron Multiplier Detector Readout Boards Using Zigzag Strips Elizabeth Starling Marcus Hohlmann Kimberley Walton, Aiwu Zhang [March 7 th , 2014]
Cost Reduction forGas Electron Multiplier Detector
Readout Boards Using Zigzag Strips
Elizabeth StarlingMarcus Hohlmann
Kimberley Walton, Aiwu Zhang[March 7th, 2014]
Introduction
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V. Bhopatkar talked about how GEM detectors work in her
presentation…
This presentation concerns one key component of these
detectors:
The readout board!
The showers pass through the three GEM foils and hit a readout board covered in gold (or solder-finish) strips. These strips are then routed to a
Panasonic connector and read out through an APV chip like the one on the right.
The Problem
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One 1m-long board…
3072 straight strips…
24 APVs!
At $150 per APV, this gets very expensivevery quickly!
The Problem
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Not just for large boards, either…
To the left: Straight strips,30 cm x 30 cm active area.
Still requires 12 APVs to read out!
All of this leads to higher cost and
a lot more clutter.
The Solution!
By using zigzag strips instead of straight
strips, the same active area can be covered
with fewer actual strips.
This means fewer APVs, less clutter, and
less cost.March 7th, 2014 Florida Academy of Sciences 5
The Program
In order to design the readout boards, we used the PCB program Altium Designer (2013).
Previously, boards had been designed using OrCAD, but this was expensive. Altium saved us $1,000.
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The Design - Beginnings
We started off with a 10 cm x 10 cm test board that had been designed in
OrCAD by a former student.
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We attempted to recreate these
dimensions for our design, which proved
somewhat of a challenge as Altium could not read the OrCAD files. We had to essentially start from
the ground up!
All unitsIn mm
The Design – CMS-Style
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Only 8 APVs are neededinstead of 24!
The Design – CMS-Style
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Specifications:
Zigzag Strips vs. Straight Strips
Strips: 1024 3072APVs: 8 24
Each section has the same number of strips, but the pitch changes, so that each strip covers
more area than in the sections below it.
1m
The Design – Test Board
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30cm x 30cm active area
Five distinct sections:1)128 10 cm-long horizontal strips2)41 30 cm-long vertical strips3)41 small-end CMS radial strips4)41 large-end CMS radial strips5)1 solid grounded area
Only two APVs are needed!
1 2
3
4
5
The Design – Test Board
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Note the difference in pitch between the large radials and the small radials. This is what accounts for the larger area covered by the larger radial zigzags.
Production
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Production
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Zigzag vs. Straight Comparison
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Left:Zigzag strips
Right:Straight strips
Difference:8 vs. 24 APVs!
Production – Warping
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Warping:0.4% - 1.2%
Goal: 0.1%
Test Results
• Testing is still ongoing. We are currently in the process of aligning the detectors, so data isn’t fully conclusive yet.
• Preliminary results show a small deterioration of spatial resolution, but not to a problematic degree – this was expected due to the increased strip size and the 1D vs. 2D readout structure.
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Cost Savings
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Cost of Equipment
1 APV Chip (128 strip channels): $1501 ADC (16 APV capacity): $2,000
Cost per Strip: $2.15
Savings for CMS-Style board
2,048 fewer strips…saves us$4,400 per board!
References
Source for image on slide #2:Murtas, F. “Development of a Gaseous Detector Based on Gas Electron Multiplier (GEM) Technology”
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