1. Micro Resistive Well Detector for Large Area Tracking
Jacquelyne Miksanek, Sarah Arends, Joseph Weatherwax
Advisor: Dr. Marcus Hohlmann, Dept. of Aerospace, Physics and Space Sciences, Florida Institute of Technology
Introduction
Micro-pattern gas detectors (MPGDs) are used to track charged particles, and are currently being used for the Large Hadron Collider (LHC) and the proposed Electron-Ion Collider (EIC). The Micro Resistive Well (μRWELL) is a newer development in this class of detectors being studied as a candidate for the future EIC. The sturdy, compact design of the μRWELL is suitable for large area tracking applications and operates efficiently in harsh radiation environments. The addition of a resistive layer mitigates the discharge issues that are common in other MPGDs, such as gas electron multipliers.
Methods
When a charged particle enters the detector, it produces preliminary ionization via collisions with charged gas molecules. Secondary ionization occurs during the single amplification stage, where a Townshend electron avalanche is produced. A series of quality control tests are conducted in order to assess the performance of the detector. The first quality control test measures the gas tightness of the detector, since a uniform gaseous medium is necessary for the signal amplification process. The second quality test analyzes the performance of the high voltage circuit and looks for any unusual activity. The third quality assesses detector efficiency by measuring the signal gain as a function of applied voltage.
Figure 1: A cross-section of the cathode and readout structure; charges amplified in the wells are collected on the DLC layer and induce a signal on the readout electrode before being sent to external readout electronics for processing.
Background
Unlike GEMs, the μRWELL detector (Figure 3) has a single amplification stage and a Diamond-Like Carbon (DLC) layer that resists spark formation. The amplification stage is manifested as a polyimide foil with a matrix of well structures (Figure 1), each containing a strong electric field that produces secondary ionization. This amplified charge is collected on the DLC and induces a signal on the readout (Figure 2). The detector has two main components: a drift cathode and a printed circuit board (PCB) readout, separated by a drift gap. The simplified design allows for a more cost efficient and time efficient assembly process.
Results
Testing showed a gas leak in the detector, the source of which is yet to be determined. Further testing is conducted under higher gas flow to compensate. Ongoing research will quantify other performance characteristics, such as signal gain.
Figure 2: A potential difference across the well structure produces a strong electric field. In the presence of such a field, a preliminary charged particle track will produce secondary ionization in the form of an electron avalanche.
References and Acknowledgements:
G. Bencivenni, et al Performance of -RWELL detector vs resistivity of the resistive stage. Nuclear Inst. and Methods in Physics Research
G. Bencivenni, et al The μ-RWELL: a compact, spark protected, single amplification-stage MPGD. International Winter Meeting on Nuclear Physics, January 2015, Bormio, Italy
G. Bencivenni, et al The μ-RWELL Layout for a High Particle Rate
Special Thank you to Laboratori Nazionali di Frascati and CERN for pioneering the Micro Resistive Well detector
Figure 3: The μRWELL detector was constructed by researchers at Florida Tech in a class 1,000 clean room.