Managing radiation degradation of CCDs on the Chandra X-ray Observatory III

O’Dell, Stephen L.; Aldcroft, Thomas L.; Blackwell, William C.; Bucher, Sabina; Chappell, John H.; DePasquale, Joseph; Grant, Catherine E.; Juda, M.; Martin, Eric R.; Minow, Joseph I.; Murray, Stephen S.; Plucinsky, Paul P.; Schwartz, D. A.; Shropshire, Dan; Spitzbart, B.; Viens, P; Wolk, S. J.

doi:10.1117/12.734594

Cited by 18 publications

(18 citation statements)

References 31 publications

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“…The Chandra radiation management plan appears to be effective at limiting ACIS exposure to damaging low energy protons. 5 The CTI increase of the FI CCDs is higher than that of the BI CCD which indicates that the accumulated radiation damage must include a mixture of particle energies, including the low energy protons which preferentially damage the FI CCDs but not the BI CCDs. Table 1 lists the initial CTI and the rate of increase after the corrections for temperature and particle background.…”

Section: Charge Transfer Inefficiencymentioning

confidence: 99%

“…Continuing exposure to both low and high energy particles over the lifetime of the mission slowly degrades the CTI further. 5,6 The two back-illuminated CCDs (ACIS-S1,S3) suffered damage during the manufacturing process and exhibit CTI in both the imaging and framestore areas and the serial transfer array. However, owing to their much deeper charge-transfer channel, BI CCDs are insensitive to damage by the low-energy protons that damage FI devices.…”

Section: Charge Transfer Inefficiencymentioning

confidence: 99%

“…9,10 Since early in the Chandra mission, procedures have been implemented that protect the focal plane instruments during times of high radiation. 5 ACIS is translated out of the focal plane, providing protection against soft protons, and is powered off. Three types of procedures are in place; planned protection during radiation-belt transits, autonomous protection triggered by the on-board radiation monitor, and manual intervention based upon assessment of space-weather conditions.…”

Section: Radiation Monitoringmentioning

confidence: 99%

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Fifteen years of the Advanced CCD Imaging Spectrometer

et al. 2014

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As the Advanced CCD Imaging Spectrometer (ACIS) on the Chandra X-ray Observatory enters its fifteenth year of operation on orbit, it continues to perform well and produce spectacular scientific results. The response of ACIS has evolved over the lifetime of the observatory due to radiation damage, molecular contamination and aging of the spacecraft in general. Here we present highlights from the instrument team's monitoring program and our expectations for the future of ACIS. The ACIS calibration source produces multiple line energies and fully illuminates the entire focal plane which has greatly facilitated the measurement of charge transfer inefficiency and absorption from contamination. While the radioactive decay of the source has decreased its utility, it continues to provide valuable data on the health of the instrument. Performance changes on ACIS continue to be manageable, and do not indicate any limitations on ACIS lifetime.

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Section: Charge Transfer Inefficiencymentioning

confidence: 99%

Section: Charge Transfer Inefficiencymentioning

confidence: 99%

Section: Radiation Monitoringmentioning

confidence: 99%

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Fifteen years of the Advanced CCD Imaging Spectrometer

et al. 2014

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“…In addition, automatic instrument saving procedures are triggered by the on-board radiation monitor and real-time space environment data. 13 The XMM-Newton EPIC instrument 14 is the telescope X-ray imager and spectrometer covering the 0.1 -15 keV energy range, and it consists of three cameras: two MOS and one pn CCD. In addition to the focal plane instrumentation, two of the three telescopes are equipped with Reflection Grating Spectrometers (RGS 15 ).…”

Section: Xmm-newton Observationsmentioning

confidence: 99%

Monte Carlo simulations of soft proton flares: testing the physics with XMM-Newton

et al. 2016

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Low energy protons (< 100 − 300 keV) in the Van Allen belt and the outer regions can enter the field of view of X-ray focusing telescopes, interact with the Wolter-I optics, and reach the focal plane. The funneling of soft protons was discovered after the damaging of the Chandra/ACIS Front-Illuminated CCDs in September 1999 after the first passages through the radiation belt. The use of special filters protects the XMM-Newton focal plane below an altitude of 70000 km, but above this limit the effect of soft protons is still present in the form of sudden flares in the count rate of the EPIC instruments that can last from hundreds of seconds to hours and can hardly be disentangled from X-ray photons, causing the loss of large amounts of observing time. The accurate characterization of (i) the distribution of the soft proton population, (ii) the physics interaction at play, and (iii) the effect on the focal plane, are mandatory to evaluate the background and design the proton magnetic diverter on board future X-ray focusing telescopes (e.g. ATHENA). Several solutions have been proposed so far for the primary population and the physics interaction, however the difficulty in precise angle and energy measurements in laboratory makes the smoking gun still unclear. Since the only real data available is the XMM-Newton spectrum of soft proton flares in orbit, we try to characterize the input proton population and the physics interaction by simulating, using the BoGEMMS framework, the proton interaction with a simplified model of the X-ray mirror module and the focal plane, and comparing the result with a real observation. The analysis of ten orbits of observations of the EPIC/pn instrument show that the detection of flares in regions far outside the radiation belt is largely influenced by the different orientation of the Earth's magnetosphere respect with XMM-Newton's orbit, confirming the solar origin of the soft proton population. The Equator-S proton spectrum at 70000 km altitude is used for the proton population entering the optics, where a combined multiple and Firsov scattering is used as physics interaction. If the thick filter is used, the soft protons in the 30-70 keV energy range are the main contributors to the simulated spectrum below 10 keV. We are able to reproduce the proton vignetting observed in real data-sets, with a ∼ 50% decrease from the inner to the outer region, but a maximum flux of ∼ 0.01 counts cm −2 s −1 keV −1 is obtained below 10 keV, about 5 times lower than the EPIC/MOS detection and 100 times lower than the EPIC/pn one. Given the high variability of the flare intensity, we conclude that an average spectrum, based on the analysis of a full season of soft proton events is required to compare Monte Carlo simulations with real events.

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“…3 Since mid-September 1999, ACIS has been protected during radiation belt passages and there is an ongoing effort to prevent further damage and to develop hardware and software strategies to mitigate the effects of radiation damage on data analysis. 4 Our primary measure of radiation damage on the CCDs is charge transfer inefficiency (CTI). The eight frontilluminated CCDs had essentially no CTI before launch, but are strongly sensitive to radiation damage from low energy protons (∼100 keV) which preferentially create traps in the buried transfer channel.…”

Section: Introductionmentioning

confidence: 99%

Using ACIS on the Chandra X-ray Observatory as a particle radiation monitor II

et al. 2012

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The Advanced CCD Imaging Spectrometer is an instrument on the Chandra X-ray Observatory. CCDs are vulnerable to radiation damage, particularly by soft protons in the radiation belts and solar storms. The Chandra team has implemented procedures to protect ACIS during high-radiation events including autonomous protection triggered by an on-board radiation monitor. Elevated temperatures have reduced the effectiveness of the on-board monitor. The ACIS team has developed an algorithm which uses data from the CCDs themselves to detect periods of high radiation and a flight software patch to apply this algorithm is currently active on-board the instrument. In this paper, we explore the ACIS response to particle radiation through comparisons to a number of external measures of the radiation environment. We hope to better understand the efficiency of the algorithm as a function of the flux and spectrum of the particles and the time-profile of the radiation event.

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Managing radiation degradation of CCDs on the Chandra X-ray Observatory III

Abstract: The CCDs on the Chandra X-ray Observatory are vulnerable to radiation damage from low-energy protons scattered off

Cited by 18 publications

References 31 publications

Fifteen years of the Advanced CCD Imaging Spectrometer

Fifteen years of the Advanced CCD Imaging Spectrometer

Monte Carlo simulations of soft proton flares: testing the physics with XMM-Newton

Using ACIS on the Chandra X-ray Observatory as a particle radiation monitor II

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