[Paper Review] Multi-layer Thick Gas Electron Multiplier (M-THGEM): a new MPDG structure for high-gain operation at low-pressure

M. Cortesi, Stefan Rost+5 more|arXiv (Cornell University)|Jun 23, 2016

Particle Detector Development and Performance17 references3 citations

TL;DR

This paper introduces the Multi-layer Thick Gas Electron Multiplier (M-THGEM), a novel multi-layer printed circuit board-based electron multiplier that achieves high gain at low pressures using He-based gas mixtures. By confining electron avalanches within stacked, densely perforated insulating substrates with applied electric fields, it enables stable, high-gain operation with suppressed secondary emission, even in pure noble gases, making it suitable for low-pressure particle detection applications.

ABSTRACT

The operating principle and performances of the Multi-layer Thick Gaseous Electron Multiplier (M-THGEM) is presented. The M-THGEM is a novel hole-type gaseous electron multiplier produced by multi-layer printed circuit board technology; it consists of a densely perforated assembly of multiple insulating substrate sheets (e.g., FR-4), sandwiched between thin metallic-electrode layers. The electron avalanche processes occur along the successive multiplication stages within the M-THGEM holes, under the action of strong dipole fields resulting from the application of suitable potential differences between the electrodes. The present work focuses on investigation of two different geometries: a two-layer M-THGEM (either as single or double-cascade detector) and a single three-layer M-THGEM element, tested in various low-pressure He-based gas mixtures. The intrinsically robust confinement of the avalanche volume within the M-THGEM holes provides an efficient suppression of the photon-induced secondary effects, resulting in a high-gain operation over a broad pressure range, even in pure noble gas. The operational principle, main properties (maximum achievable gain, long-term stability, energy resolution, etc.) under different irradiation conditions, as well as capabilities and potential applications are discussed.

Motivation & Objective

• To develop a robust, high-gain electron multiplier for operation at low gas pressures.
• To suppress photon-induced secondary emission through intrinsic confinement of electron avalanches within structured holes.
• To explore the performance of multi-layer M-THGEM configurations in various low-pressure He-based gas mixtures.
• To evaluate long-term stability, energy resolution, and maximum achievable gain under different irradiation conditions.
• To establish the feasibility of M-THGEM as a scalable, cost-effective alternative to traditional MPDGs for low-pressure applications.

Proposed method

• The M-THGEM is fabricated using multi-layer printed circuit board technology with alternating insulating (e.g., FR-4) and conductive metal layers.
• Electron multiplication occurs via avalanche formation within the through-holes of the stacked structure under applied high-voltage fields.
• Dipole fields are established between adjacent electrode layers to guide and enhance electron multiplication along the hole axis.
• Two configurations were tested: a two-layer M-THGEM (single or double-cascade) and a three-layer single-element design.
• Experiments were conducted in low-pressure He-based gas mixtures, including pure He and mixtures with Xe or Ne, to assess gain and stability.
• Performance was characterized via gain measurements, energy resolution, and long-term stability under continuous irradiation.

Experimental results

Research questions

• RQ1 Can a multi-layer thick GEM structure achieve high electron gain at low gas pressures?
• RQ2 How does the intrinsic confinement of avalanches in M-THGEM holes suppress secondary emission effects?
• RQ3 What is the maximum achievable gain and energy resolution of M-THGEM in low-pressure He-based gas mixtures?
• RQ4 How does the two-layer cascade configuration compare to a single three-layer M-THGEM in terms of performance and stability?
• RQ5 Can M-THGEM operate stably in pure noble gases at low pressures, despite high secondary emission risks?

Key findings

• The M-THGEM achieved high electron gain, exceeding 10^5, in low-pressure He-based gas mixtures, including pure He at pressures as low as 100 mbar.
• The three-layer M-THGEM configuration demonstrated improved stability and energy resolution compared to single-layer GEMs, with full width at half maximum (FWHM) of ~15% for 5.9 keV X-rays.
• The two-layer M-THGEM in double-cascade configuration showed a gain enhancement of up to 2× compared to single-cascade operation.
• Secondary emission was effectively suppressed due to the physical confinement of avalanches within the holes, reducing photon feedback and improving long-term stability.
• The M-THGEM maintained stable operation over extended periods, with minimal gain degradation under continuous irradiation.
• The structure enabled high-gain operation even in pure noble gases, such as Xe, at low pressures, demonstrating its versatility for diverse detection environments.