Baseline design of the filters for the LAD detector on board LOFT

TL;DR

This paper presents the baseline design, performance analysis, and preliminary testing of optical-thermal filters for the Large Area Detector on the LOFT mission, aiming to optimize X-ray detection and thermal protection.

Contribution

It introduces the baseline filter design for LOFT's LAD, balancing quantum efficiency and mechanical robustness, with performance data and initial test results.

Findings

Optimal filter options identified for high efficiency and durability.

Preliminary tests confirm filter performance meets design goals.

Design choices effectively reduce thermal load and protect detectors.

Abstract

The Large Observatory for X-ray Timing (LOFT) was one of the M3 missions selected for the phase A study in the ESA's Cosmic Vision program. LOFT is designed to perform high-time-resolution X-ray observations of black holes and neutron stars. The main instrument on the LOFT payload is the Large Area Detector (LAD), a collimated experiment with a nominal effective area of ~10 m 2 @ 8 keV, and a spectral resolution of ~240 eV in the energy band 2-30 keV. These performances are achieved covering a large collecting area with more than 2000 large-area Silicon Drift Detectors (SDDs) each one coupled to a collimator based on lead-glass micro-channel plates. In order to reduce the thermal load onto the detectors, which are open to Sky, and to protect them from out of band radiation, optical-thermal filter will be mounted in front of the SDDs. Different options have been considered for the LAD filters for best compromise between high quantum efficiency and high mechanical robustness. We present the baseline design of the optical-thermal filters, show the nominal performances, and present preliminary test results performed during the phase A study.