2017 G 4 SUW 10 12 April University

2017 G 4 SUW, 10 -12 April, University of Surrey, Guildford, UK Simulations for WXT aboard Einstein Probe mission with Geant 4 Donghua Zhao, Chen Zhang, Weimin Yuan National Astronomical Observatories, Chinese Academy of Sciences (NAOC)

Einstein Probe (EP) u An X-ray focusing telescope with very wide FOV u. Proposed by NAOC, IHEP (Chinese Academy of Sciences (CAS) institutes) u. Currently under final review formal approval, engineering expected to start this year u. Launch Time: 2021/22 2

Scientific Objectives of EP 1. Systematic surveys of X-ray transients at unprecedented sensitivity, detect faint X-ray transients and find new types of transients. 2. Reveal quiescent black holes by catching their X-ray flares 3. Detect electromagnetic wave counterparts of gravitational wave events and precisely locate them. 3

Instruments on EP and MPO FXT WXT o Wide-field X-ray telescope o Follow-up X-ray telescope very light , make large FOV possible 4

Main Characteristics u A focusing telescope with largest FOV : 60 o X 60 o u Energy Range: 0. 5 -4 ke. V u most sensitive all-sky monitor 5

Simulations for WXT with Geant 4. 9. 6 p 02 1. Build Monte Carlo model 2. Simulations on the performance of the optical system 3. Instrumental background simulations 6

WXT model with Geant 4 F r am e he rs ld cto Shie te t om De B ot ll su rro un din g. S sur hie rou ld nd ing Shi eld M PO WXT and Platform Physics processes 7

X-ray reflection at grazing angles u Use XRTG 4 developed by Buis and Vacanti in the program based on Geant 4. u Q: an independent software developed by professor Willingale at LE University u Results from Geant 4 and Q agree well with each other with an averaged deviation < 3%. Donghua Zhao, et al. , 2017 8

PSF and effective area of WXT 9

Simulated sky observations Donghua Zhao, et al. , 2017 point sources from RASS Bright Source Catalogue 10

Background Simulations

Background sources Cosmic Particles X rays total Soft X-rays NH=3 E 20 cm^2 Campana, R. et al. 2013 Zhao D. et al. 2012 and Miyaji T. et al. 1998 12

Background due to different source 13

Impact of Grazing Reflection on BKG Without grazing reflection Physics process Without grazing scattering With grazing reflection Energy range Total (cts/s/cm^2) X rays Particles 0. 5 -4 ke. V 0. 043 0. 027 0. 016 0. 5 -4 ke. V 0. 187 0. 173 0. 014 14

CMOS detector of WXT e g S hie ld F r am hie l d din Al Film ro un su r rs he ll ld cto Shie Substrate Si De te om Sensitive Si din g. S sur rou n B ot t M PO 15

Impact of detector thickness on background 10 um 30 um Thickness X rays Particles Total(cts/s/cm^2) 10 um 0. 180 0. 108 (37 %) 0. 288 30 um 0. 156 0. 001 (0. 4%) 0. 157 16

Summary u. EP will be an X-ray focusing telescope with largest FOV, and a most sensitive all-sky monitor. u. Built a Monte Carlo model for WXT u. Studied WXT’s performance including the PSF, effective area, background, etc. 17

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Shield of WXT F r am e M PO Pb Cu C Al C Cu Shie ld cto om De te B ot t rs he ll su r ro un sur r din g oun Sh iel d din g S hie ld Outside -> Inside 19