Cost Reduction for Gas Electron Multiplier Detector Readout Boards Using Zigzag Strips Elizabeth Starling Marcus Hohlmann Kimberley Walton, Aiwu Zhang [March 7 th, 2014]

Introduction March 7th, 2014Florida Academy of Sciences2 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 March 7th, 2014Florida Academy of Sciences3 One 1m-long board… 3072 straight strips… 24 APVs! At $150 per APV, this gets very expensive very quickly!

The Problem March 7th, 2014Florida Academy of Sciences4 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, 2014Florida Academy of Sciences5

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. March 7th, 2014Florida Academy of Sciences6

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. March 7th, 2014Florida Academy of Sciences7 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 units In mm

The Design – CMS-Style March 7th, 2014Florida Academy of Sciences8 Only 8 APVs are needed instead of 24!

The Design – CMS-Style March 7th, 2014Florida Academy of Sciences9 Specifications: Zigzag Strips vs. Straight Strips Strips: APVs: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 March 7th, 2014Florida Academy of Sciences10 30cm x 30cm active area Five distinct sections: 1) cm-long horizontal strips 2)41 30 cm-long vertical strips 3)41 small-end CMS radial strips 4)41 large-end CMS radial strips 5)1 solid grounded area Only two APVs are needed!

The Design – Test Board March 7th, 2014Florida Academy of Sciences11 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 March 7th, 2014Florida Academy of Sciences12

Production March 7th, 2014Florida Academy of Sciences13

Zigzag vs. Straight Comparison March 7th, 2014Florida Academy of Sciences14 Left: Zigzag strips Right: Straight strips Difference: 8 vs. 24 APVs!

Production – Warping March 7th, 2014Florida Academy of Sciences15 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. March 7th, 2014Florida Academy of Sciences16

Cost Savings March 7th, 2014Florida Academy of Sciences17 Cost of Equipment 1 APV Chip (128 strip channels): $150 1 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” March 7th, 2014Florida Academy of Sciences18