Cost Reduction for Gas Electron Multiplier Detector Readout Boards Using Zigzag Strips

1. Cost Reduction forGas Electron Multiplier DetectorReadout Boards Using Zigzag Strips Elizabeth Starling Marcus Hohlmann Kimberley Walton, Aiwu Zhang [March 7th, 2014]

2. Introduction 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. Florida Academy of Sciences

3. The Problem One 1m-long board… 3072 straight strips… 24 APVs! At $150 per APV, this gets very expensive very quickly! Florida Academy of Sciences

4. The Problem 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. Florida Academy of Sciences

5. 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. Florida Academy of Sciences

6. 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. Florida Academy of Sciences

7. The Design - Beginnings We started off with a 10 cm x 10 cm test board that had been designed in OrCADby a former student. 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 Florida Academy of Sciences

8. The Design – CMS-Style Only 8 APVs are needed instead of 24! Florida Academy of Sciences

9. The Design – CMS-Style Specifications: Zigzag Strips vs. Straight Strips Strips: 1024 3072 APVs: 8 24 1m 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. Florida Academy of Sciences

10. The Design – Test Board 30cm x 30cm active area Five distinct sections: 128 10 cm-long horizontal strips 41 30 cm-long vertical strips 41 small-end CMS radial strips 41 large-end CMS radial strips 1 solid grounded area Only two APVs are needed! 3 1 2 4 5 Florida Academy of Sciences

11. The Design – Test Board 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. Florida Academy of Sciences

12. Production Florida Academy of Sciences

13. Production Florida Academy of Sciences

14. Zigzag vs. Straight Comparison Left: Zigzag strips Right: Straight strips Difference: 8 vs. 24 APVs! Florida Academy of Sciences

15. Production – Warping Warping: 0.4% - 1.2% Goal: 0.1% Florida Academy of Sciences

16. 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. Florida Academy of Sciences

17. Cost Savings 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! Florida Academy of Sciences

18. References Source for image on slide #2: Murtas, F. “Development of a Gaseous Detector Based on Gas Electron Multiplier (GEM) Technology” Florida Academy of Sciences