HE instrument and in-orbit performance Yifei. Zhang On behalf of HE Group in HXMT, IHEP, 2018.4.10

Main contents Outline HE Instrument and in-orbit performance High Energy Detector Anti-Coincident Detector Automatic Gain Control System Particle Monitor

Outline High Energy X-ray Telescope (HE) Consisting of High Energy Detector (HED), Particle Monitor (PM), Automatic Gain Control System (AGC), Anti-Coincident Detector (ACD), Collimator, and electronic system. Main characteristics Total detection area ~5000 cm^2 Covering 20-250 keV X/γ Field of view 15：1.1×5.7 deg^2 2：5.7×5.7 deg^2 1：Covered with Tantalum Energy resolution ≤19% @59.5keV High Energy X-ray Telescope is the main payload. (Side)

Outline X/γ ray Detection and charged particle rejection X/γ X/γ rays in FOV will be absorbed by NaI(Tl) crystal and treated as effective events. X/γ rays coming from the back will be absorbed by CsI(Na) crystal. Those events can be rejected by PSD method in off-line processing. Charged particles can be rejected by ACD. X/γ X/γ e, p, … X/γ e, p, …

HE Instrument and in-orbit performance High Energy Detector (HED) NaI(Tl)/CsI(Na) phoswich detector Detecting 20-250 keV X/γ rays ≤19% @ 59.5 keV Be made up of Beryllium, 1.5mm thick NaI(Tl), φ190 mm×3.5 mm CsI(Na), φ190 mm×40 mm Quartz glass PMT R877, gain ~1.0×10^5 Shock absorber Magnetic shield Charge sensitive amplifier, output a voltage pulse with a width less than 3 μs. Array with 18 HEDs, total ~ 5000 cm^2 Shock absorber

HED In-orbit performance Light curve Energy spectrum Pulse width spectrum Time interval spectrum CsI(Na) NaI(Tl) 2μs 6μs

HED Redistribution Matrix Function (RMF) Get the in-orbit RMF on the base of background calibration Use Crab source to check and improve it. More details in upper report ‘Insight-HXMT calibration’

HE Instrument and in-orbit performance Anti-Coincident Detector (ACD) Including 6 top-ACDs and 12 side-ACDs, plastic detector Detecting charged particle and giving a mark for rejection. Mainly made up of Plastic wrapped with reflector PMT followed by divider Absorber and shield Charge sensitive amplifier Absorber, EM shield ACD (Side) ACD (Top)

ACD Anti-Coincident Detector (ACD) Plastic in top-ACD responding to HED field of view is designed to be 3.4 mm thick to enhance the transmission of X/γ rays. Other area is 6.4 mm thick as well as in side-ACD. Plastic: 3.4 mm thick Top-ACD Side-ACD Plastic: 6.4 mm thick

ACD Veto efficiency Average ~ 22% in all channel

HE Instrument and in-orbit performance Automatic Gain Control System (AGC) To reduce the effect caused by the change of temperature and magnetic field to keep HED working steady. Located at the bottom of Collimator and near to the beryllium of HED. MPPC, size 3×3 mm Am-241, ~ 200 Bq Readout electronics AGC MPPC AGC MPPC PCB PMT Collimator NaI(Tl)/CsI(Na) Tagged alpha source

AGC Automatic Gain Control logic Increase the PMT voltage of 312 mV when pulse height of a gamma ray coming from Am-241 tagged in AGC is lower than 50 channel. If not decrease 312 mV. Reference Channel P0 Measured P Left window Right window

HE Instrument and in-orbit performance Particle Monitor (PM) Plastic detector Monitoring the intensity of in-orbit charged particles Warning to shut down other detectors’ power Be made up of Plastic, φ1cm × 1cm PMT, R647-1 Shock absorber Magnetic shield Divider Charge sensitive amplifier Threshold Electron, ≥1MeV Proton, ≥ 20MeV PM outline Plastic PMT absorber shield divider Amplifier

PM Particle distribution in HXMT orbit SAA

Summary Parameters Design Value In orbit performance Detection area ~5000 cm^2 5100 cm^2 Energy range 20-250 keV ~ 18-300 keV @ normal mode by NaI(Tl) ~ 100-3300 keV @ GRB mode by CsI(Na) * Resolution ≤19% @ 59.5keV ~ 17% @ 59.5keV (estimated) Spatial resolution 1.1 deg ×5.7 deg, 5.7 deg ×5.7 deg Time resolution ≤ 25 μs 2 μs Dead time ~ 6 μs (without big signals contribution) *: GRB mode is an expanded working mode by using the CsI(Na) crystal with a lower PMT supply voltage.

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