Koji Mori (University of Miyazaki) Y. Nishioka , S. Ohura , Y. Koura, M. Yamauchi ( miyazaki ),

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Proton Radiation Damage Experiment on P-Channel CCD for X-ray CCD camera onboard the Astro -H satellite. Koji Mori (University of Miyazaki) Y. Nishioka , S. Ohura , Y. Koura, M. Yamauchi ( miyazaki ), H. Nakajima, S. Ueda, H. Kan, K. Hayashida , N. Anabuki , H. Tsunemi (Osaka), - PowerPoint PPT Presentation

Transcript of Koji Mori (University of Miyazaki) Y. Nishioka , S. Ohura , Y. Koura, M. Yamauchi ( miyazaki ),

PowerPoint Presentation

Proton Radiation Damage Experiment on P-Channel CCD for X-ray CCD camera onboard the Astro-H satelliteKoji Mori (University of Miyazaki)Y. Nishioka, S. Ohura, Y. Koura, M. Yamauchi (miyazaki), H. Nakajima, S. Ueda, H. Kan, K. Hayashida, N. Anabuki, H. Tsunemi (Osaka), T. Kohmura, S. Ikeda (Kogakuin), H. Murakami (Rikkyo)T. Dotani, M. Ozaki (ISAS/JAXA), Y. Maeda (Miyazaki), and K. Sagara (Kyushu)1ContentsP-channel CCD for the Astro-H satelliteProton radiation damage experimentComparison with other P-channel CCD experimentsSummary

2012-09-03/07PIXEL20122/202012-09-03/07PIXEL20122012-09-03/07PIXEL2012I first explain our new P-channel CCD for the Astro-H satellite as an introduction of my talk and next give you a detail of experiment and result. Then I briefly discuss the results comparing other P-channel CCD experiments. I summarize my talk at the last. OK, lets move on the introduction part.2X-ray CCD for Astronomical useA standard focal-plane detector with a 20-year history ASCA (1993-2001): N-channel Front-Illuminated CCD Suzaku (2005- ): N-channel Back-Illuminated CCDAstro-H (2014- ): P-channel Back-Illuminated CCD 2012-09-03/07PIXEL20123/20

ASCA 1993, 417kg

SUZAKU 2005, 1700kg

ASTRO-H 2014, 2700kgCross-sectionof CCDelectroden-channelp-type Sin-type Sip-channelFirst I show you how X-ray CCD is evolving for astronomical use. An X-ray CCD has been a standard focal-plane detector having a 20-year history in X-ray astronomy. We have flown five X-ray astronomical satellites until now and plan to launch a new one two years later from now. CCD detectors have been used from the 4th satellite ASCA, and it starts as N-ch FI CCD. Then the currently flying 5th satellite Suzaku newly carries a N-ch but BI CCD. Finally, for the coming 6th satellite Astro-H, we reached to a new, much thicker P-ch BI CCD.3

New P-channel CCD for New SatelliteHAMAMATSU PHOTONICS K.K.-provided CCD-NeXT4frame-transfer type, fully-depleted BI CCD with a depletion layer thickness of 200 m24 m pixel size with a 1280x1280 format -> 640x640 after 2x2 on-board binning2 readout nodes used2012-09-03/07PIXEL20124/20Imaging Area31mm x 31mmStorage Areacovered when installedThis is a photo of our new P-ch CCD and this is a schematic view of the CCD. Its physical dimension is 30x60mm but this is frame-transfer type so that top half is imaging area and the bottom half is storage area. The storage area is covered when this is installed into the camera. There are two readout nodes. The pixel size is 24 um with a 1280x1280 format. However, since we use 2x2 on-board binning, you will see a 640x640 formant in the data.4

Radiation damage in spaceCosmic-ray protons are the primary source for damage2012-09-03/07PIXEL20125/20

XYYPulse Height (Q)

Charge Transfer inefficiency (CTI) is a measure of the radiation damage of CCDStacking plotwith 55FeFrame imageOne of the things we have to care about is radiation damage in space. This is a real frame image taken by Suzaku CCD. Cosmic-ray protons are the primary source for damage. Then, CTI is a measure of the radiation damage of CCD. It is a fraction of a charge loss in one transfer and defined in this equation. In order to measure CTI, you need to irradiate X-rays with know energy at whole area. We usually used 55Fe. Then, you will have this stacking plot where the pulse height, a signal charge of each pixel, is shown as a function of Y coordinate, namely half of the number of transfer. Before damage, you see a flat bar. However, once CCD is damaged, the bar has a slope because some changes are lost during transfer. CTI is almost equal to the slope. 5Mitigation of radiation damageCharge-Injection techniqueCharges are intentionally injected to selected rows which are regularly spaced The injected charges work as scarifies to fill traps and following real X-ray-induced charges are transferred smoothlyOptimizing temperaturetimescales of trapping and de-trapping depend on temperatureCCD typeIt is reported that P-ch CCD is more radiation tolerant2012-09-03/07PIXEL20126/20

http://heasarc.gsfc.nasa.gov/docs/suzaku/analysis/sci.htmlFor space use, we need to know how radiation hard our new device is andhow mitigation methods workThere are several ways to mitigate radiation damage. Among them, CI technique is unique. This figure shows its idea. In this technique,

Optimizing temperature also work fine because CCD type may be a key

so we performed a proton radiation damage experiment.6ContentsP-channel CCD for the Astro-H satelliteProton radiation damage experimentComparison with other P-channel CCD experimentsSummary2012-09-03/07PIXEL20127/20

InawashiroFukuokaNaritaMiyazakiI give you a detail of BTW, this is a map of Japan.7FacilityKyushu University tandem accelerator laboratoryperformed from 2012 February 1st through 5thProton beam we usedEnergy: 10.5 MeVIntensity: 50nA - 1uAguided into the scattering chamber 2012-09-03/07PIXEL20128/20


We performed an experiment at Kyushu University tandem accelerator laboratory from 2012 This is a schematic view of this facility. This is a H- ion generator. The ions are extracted to the tandem accelerator and boosting up to high energy protons.8

Setup in the scattering chamberScattered beam is usedDirect beam intensity too strong for our purposeScattered beam is more spatially uniform Carbon target is selectedThe first excited state is about 4.4 MeV, allowing us to easily remove inelastic scattered protons with a thin filterIncoming protons are mono-energetic, 6.70.5(HWHM) MeV


This is a setup in the scattering chamber. The beam is coming from left hand side in this figure and photo, and is scattered in the central target. Our CCD is located at a right angle, bottom in this figure. Beam condition is monitored by FC that is on the beam path and also by SSD put aside our CCD and at an opposite position.

10nA, even if the beam size is spatially uniform, is equivalent to 220 yr9

We used two types of CCDLarge format CCDinstalled in a camera body attached at the side of the chamberworking at -110 degree Celsius during beam-onMini-size CCDsame type as the large format CCD, just smallsimply exposed inside the chamber, not working during beam-onmuch closer to the scattering point, larger flux compared to the LF CCD2012-09-03/07PIXEL201210/20

10nA, even if the beam size is spatially uniform, is equivalent to 220 yr10Why 6.7 MeV?6.7 MeV protons penetrate 200 m silicon CCD Their dE/dx is more or less constant along the depth direction, damaging the chip uniformly in the depth direction.The deposit energy is about 2.7 MeV2012-09-03/07PIXEL201211/20

Bragg curve of protons of various energy in SiliconThey are the Bragg curves 11Dose rate in orbitLeft: day-averaged radiation environment modeled in the orbit of the Astro-H satellite~100 MeV protons in SAA are the major source of damaging CCDRight: Proton flux after passage of the camera body and Deposited energy spectrumthe camera body is simplified into Al 20mm in our calculationThe dose rate is 2.1x106 MeV cm-2 day-1 or 260 rad yr-12012-09-03/07PIXEL201212/20

Mizuno et al. (2010, SPIE, 7732,105)Since we are interested in how long our CCD survives in space, we need to calculate dose rate in orbit12Stacking plotsCTI is increased after irradiationActivating the CI function mitigates the increase of CTIA saw-tooth shape appears in stacking plots2012-09-03/07PIXEL201213/20

without CIwith CIBeforeAfterThey are example stacking plots before and after experiment. left-hand and right-hand sides shows those without and with CI technique, respectively. It is clear that CTI is increased, slope gets steeper, after irradiation. And it might be less clear to you in this plot but activating With CI technique, a characteristic saw-tooth shape appears in stacking plot because the closer to the CI row the higher the trap-filling effect is.

Even focusing on a specific transfer row, scatter of PHA becomes large13Degradation without CIThe degradation of our new P-ch CCD in terms of CTI is comparable with that of the N-channel CCD onboard the Suzaku satellite, confirming its radiation tolerance enough for space use 2012-09-03/07PIXEL201214/20

This plot shows CTI as a function of time equivalent in orbit that is converted from the number of protons irradiated. As you can see, in our setup, 10^9 protons are approximately equivalent to 3 year in orbit Red and blue points show the results form LF CCD while green one comes from mini-CCD. Black dots indicate CTI values obtained from CCD onboard Suzaku so that they are measured one actually obtained in orbit. From this plot, 14Degradation with CIThe same conclusion does apply also for the case with CIActivating CI function surely mitigates CTI degradation 2012-09-03/07PIXEL201215/20

This plot is the same with previous one but with CI technique. 15Temperature dependenceperformed after the radiation damage experimentThe cooler is the bettermore than factor 2 improvement at -140 degree Celesius2012-09-03/07PIXEL201216/20

CI-onCI-offworking temperatureat the radiation testWe performed temperature dependence test after radiation damage experiment, just measuring CTI at various temperature. 16ContentsP-channel CCD for the Astro-H satelliteProton radiation damage experimentComparison with other P-channel CCD experimentsSummary

2012-09-03/07PIXEL201217/20Comparison with other experimental resultsReported values of LBNL P-ch CCDs show higher radiation toleranceEven considering differences in experimental setup (6.7 vs 12 MeV, -110 vs -145 degC), the difference appears to remainDifferent manufactures (processing) might result in the difference


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