High-resolution scanner for micropattern gaseous detectors

The purpose of the device is to measure detailed physical properties of micropattern gaseous detectors (e.g. GEM, THGEM). The micropattern detector technology is very popular nowadays, on one hand in CERN experiments will be applied (e.g. ALICE, CMS, ATLAS etc.) but beyond basic research there are more and more practical applications as well. This detector technology is relatively new (F. Sauli, 1997) therefore parameter fine-tuning and optimizations are open questions as well as production faults and the effect on the detector performance is not fully understood. The LEOPARD project has been created to answer these questions.

The operating principle of the LEOPARD device is that stepper motors move an optical head above the area to be examined, then we scan this area (Fig. 1). The optical head contains a microscope camera for visual check and a UV light source for excitation of the area. The UV light is focused to a spot on the GEM’s surface which excites a photoelectron, then it will be gained and measured. From the examined area we create photoelectron and gain maps (Fig. 2), these parameters help us investigate the physical properties of the GEM.

With this device we could find answer to really important questions: What are the effects of the geometric parameters to the gain? How does the “chargeup” effect changes the gain? What are the effects of production faults to the operation of GEMs? Beyond the upgrade of the device there are ongoing researches on these issues in the group.


Fig. 1. The structure of the Leopard scanner.

Leopard Maps

Fig. 2. Left to right: microscope image of a TGEM, a Photoelectron and a Gain map [1].

Main financial support: AIDA-2020 No. 654168, furthermore part of the RD51 collaboration.

[1] G. Hamar, D. Varga: High resolution surface scanning of Thick-GEM for single photo-electron detection;
NIM A 694, p 16-23 (2012.12.)

Author: Gábor Nyitrai