Development of the Soft X-ray Large solid angle Camera onboard WF-MAXI H. Tomida (ISAS/JAXA), S. Imai (Tokyo Tech, ISAS/JAXA) N. Isobe, N. Kawai, Y. Yatsu (Tokyo Tech) T. Kohmura, K. Tamasawa, Y. Ozawa, K. Yasuda (Tokyo Univ. of Science) M. Arimoto (Waseda, Univ.), H. Tsunemi (Osaka Univ.) T. Mihara, M. Serino (RIKEN), and the SLC team. 5th annual symposium of the innovarive area 2016/12/26

Soft X-ray Large solid angle Camera (SLC) WF-MAXI/SLC on iSEEP/ISS Mission instrument of WF-MAXI Science goal: Monitoring soft X-ray transients, especially counterparts of gravitational wave events. Specifications Energy range: 0.7 – 10 keV Position localization: 0.1 deg Field of View: > 10 % of the entire sky 60 deg x 60 deg (TBD) Sensitivity: 100 mCrab in 100 s (5s) Effective area: 293 cm2 Detector system 2 units of CCD arrays with 1-d coded masks (X and Y directions) 380 mm Coded Mask (Heritage of HETE-2) 250 mm CCD chip (behind the mask) 5th annual symposium of the innovarive area 2016/12/26

Soft X-ray Large solid angle Camera (SLC) CCDs for SLC Fabricated by the Hamamatsu photonics P-ch back-illuminated chip 16 CCDs in total (8 for each array) Format: 2048 (H) x 3668 (V), 15 mm pixel CCD operation Flexible drive/read-out patterns with m- code Read out in parallel sum mode Read out time; 0.1 s Heritage MAXI/SSC: readout/drive electronics ASTRO-H/SXI: CCD, m-code, camera CCD cooling system: 2 options Mechanical cooler CCD temperature: -100 ℃ Flight proven High cost Radiator + peltier CCD temperature: ≾−90 ℃ Low cost V CCD Flexible cable Connector SLC thermal design (Mechanical cooler) -109 109 Temperature [℃] CCDs: -100℃ 5th annual symposium of the innovarive area 2016/12/26

Ground performance of the SLC CCD 55Fe spectrum @ CCD -90℃ Energy resolution ∼𝟏𝟖𝟎 eV for 5.9 keV Similar to ASTRO-H/SXI (∼𝟏𝟔𝟎 eV, -110 ℃) Further improvement is possible Small pixel size SLC: 15 mm ASTRO-H: 24 mm Fewer single pixel events Binning parameters to be optimized Mn Kα Mn Kβ Without radiation damage, the SLC CCD exhibits a good performance at -90 ℃. 5th annual symposium of the innovarive area 2016/12/26

Radiation damage on the SLC CCDs The CCD is expected to be degraded by radiation damage. To check -90 ℃ performance. Radiation damage test HIMAC (Heavy Ion Medical Accelerator in Chiba) 1st round : 2015 Dec 9 – 19 ASTRO-H CCD (already reported) 2nd round : 2016 Feb 22 - Mar 2 WF-MAXI/SLC CCD The CCD was irradiated with the scattered beam. Direct beam: too strong Scattered beam: spatially uniform. The CCD was operated at -80 ℃, during proton irradiation. The concept of “test like you fly” Protons beam Vacuum Chamber Scattered Protons Faraday cup Incident proton beam Energy: 6 MeV Intensity: 70uA-400uA Mini-type SLC CCD 5th annual symposium of the innovarive area

Results: Charge Transfer (In-)Efficiency (CTE/CTI) one of the most impotent parameter to evaluate the CCD performance. Before irradiation SLC CCD: CTE ~100% better than ASTRO-H CCD After irradiation The CTE of the WF-MAXI CCD is similar to that of ASTRO-H CCD (or possibly better) -90 ℃ ASTRO-H CCD ( -110℃) 1.0 – CTE (CTI) 0.1year 1year 10year Proton dose [cm-2] note : In orbit, the CTE/CTI correction is not applicable to the SLC CCD, since the CTE/CTI is unable to be measured in the operation mode of the SLC CCD.

Results: Dark current -90 ℃ The MAXI/SSC has suffered from the increased dark current in orbit. 7 years operation CCD temperature: -60 ℃ SLC CCD design To minimize the dark current Results of WF-MAXI CCD 8 years irradiation in the ASTROH orbit CCD temperature: -90 ℃ 0 week 1 week 1 month 6 month 1 year 3 years 8 years dark current (e- s-1 4pix-1) -90 ℃ time [s] after the beam irradiation We confirmed that the dark current after the 8 years-operation is very small, 2−3 e- s-1 4pix-1, as far as the CCD is cooled down to below -90 ℃ (possibly better than the ASTRO-H CCD level @ -110℃) is expected to have no significant impact on the energy resolution and dynamic range.

SLC Bread Board Model (BBM) Electronics SLC chamber One CCD was installed inside the SLC chamber Plastic cover The set up of the SLC BBM was completed last week. The basic operation of the m-code in the drive electronics has been confirmed. We plan to evaluate the performance of the CCDs using this SLC BBM, by the end of this fiscal year. Cooler module (non-flight item) ～1 m 5th annual symposium of the innovarive area 2016/12/26

Summary The introduction to the WF-MAXI/SLC and its development status are presented. SLC: CCD arrays + coded mask Soft band (0.7 – 10 keV), good position localization (0.1 deg) wide field of view (10% of the sky), high sensitivity (100 mCrab) Heritages MAXI/SSC: readout/drive electronics ASTRO-H SXI: HETE-2: coded mask The radiation damage on the SLC/CCDs was evaluated. The CCD performance without radiation damage was confirmed to be good. The CTE and dark current (@ -90℃) were measured as similar to (or even better than) those of the ASTRO-H CCDs By using the BBM, we are on the way to demonstrate the SLC performance. The flexibility of the CCD readout/drive patterns with the m-code was confirmed. The evaluation is planed to be completed by the end of this fiscal year. 5th annual symposium of the innovarive area 2016/12/26