Modeling of proton-induced CCD degradation in the Chandra X-ray Observatory

Lo, D. H.; Srour, J. R.

doi:10.1109/tns.2003.820735

Cited by 24 publications

(16 citation statements)

References 15 publications

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“…The magnets are assumed to be characterized by an uniform magnetization M. In order to generate an intense field, hard magnetic materials, like Samarium-Cobalt magnets (SmCo 5 (right) The profile of the magnetic field intensity in the mid-plane, along a median sector, where the magnetic field has the minimum intensity. The radial extension of the field is sufficient to cover the radii of the SIMBOL-X mirrors.…”

Section: A Possible Design For the Simbol-x Proton Divertermentioning

confidence: 99%

“…At that time, the unwanted capability of the X-ray mirror assembly to reflect and focus high-energy particles -in addition to X-rays -was underestimated, therefore the ACIS had been effectively shielded against particle background from all direction, but that of the mirrors. The range of soft protons in Silicon (0.92 µm for 100 keV protons 5 ) is sufficient for them to traverse the top layers of the CCD and create charge traps in the sensitive region, resulting in an energy sensitivity degradation. In particular, for Chandra's ACIS detector the most dangerous protons seemed to be those with kinetic energies from 100 to 200 keV 6 .…”

Section: Introductionmentioning

confidence: 99%

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A magnetic diverter for charged particle background rejection in the SIMBOL-X telescope

Spiga

Fioretti²,

Bulgarelli³

et al. 2008

Space Telescopes and Instrumentation 2008: Ultraviolet to Gamma Ray

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Minimization of charged particle background in X-ray telescopes is a well known issue. Charged particles (chiefly protons and electrons) naturally present in the cosmic environment constitute an important background source when they collide with the X-ray detector. Even worse, a serious degradation of spectroscopic performances of the X-ray detector was observed in Chandra and Newton-XMM, caused by soft protons with kinetic energies ranging between 100 keV and some MeV being collected by the grazing-incidence mirrors and funneled to the detector. For a focusing telescope like SIMBOL-X, the exposure of the soft X-ray detector to the proton flux can increase significantly the instrumental background, with a consequent loss of sensitivity. In the worst case, it can also seriously compromise the detector duration. A well-known countermeasure that can be adopted is the implementation of a properly-designed magnetic diverter, that should prevent high-energy particles from reaching the focal plane instruments of SIMBOL-X. Although Newton-XMM and Swift-XRT are equipped with magnetic diverters for electrons, the magnetic fields used are insufficient to effectively act on protons. In this paper, we simulate the behavior of a magnetic diverter for SIMBOL-X, consisting of commercially-available permanent magnets. The effects of SIMBOL-X optics is simulated through GEANT4 libraries, whereas the effect of the intense required magnetic fields is simulated along with specifically-written numerical codes in IDL.

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Section: A Possible Design For the Simbol-x Proton Divertermentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

A magnetic diverter for charged particle background rejection in the SIMBOL-X telescope

Spiga

Fioretti²,

Bulgarelli³

et al. 2008

Space Telescopes and Instrumentation 2008: Ultraviolet to Gamma Ray

View full text Add to dashboard Cite

show abstract

“…A detailed modeling of the NIEL damage by low energy protons to Chandra ACIS is reported in [3]. The most sensitive region of the CCD, i.e., the buried channel is at a silicon equivalent depth of m to the incident protons, i.e., it is behind the optical filter and the top layers of the CCD for the front illuminated case.…”

Section: Introductionmentioning

confidence: 99%

“…The most sensitive region of the CCD, i.e., the buried channel is at a silicon equivalent depth of m to the incident protons, i.e., it is behind the optical filter and the top layers of the CCD for the front illuminated case. The range of 100 keV protons in silicon is in the order of 0.92 m [3], [4], thus only incident protons with energy above 100 keV can reach the sensitive region of the CCD and cause damage. The fact that the incident proton spectrum is very steep [3]- [5], implies that the majority of the damaging protons are of energy just above keV.…”

Section: Introductionmentioning

confidence: 99%

Update on the use of Geant4 for the Simulation of low-energy protons scattering off X-ray Mirrors at grazing incidence angles

Lei

Nartallo²,

Nieminen

et al. 2004

IEEE Trans. Nucl. Sci.

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A new physics process has been implemented in the Geant4 Monte Carlo code to treat the scattering of low-energy protons at grazing incidence angles. Experimental data has shown that this is a predominantly surface process where protons are reflected without entering the surface material hence the classical multiple scattering process is not applicable. The new model has been used to revise predictions of proton fluence at the focal plane of the XMM-Newton telescope obtained in earlier simulations. Index Terms-Geant4Monte Carlo code, XMM-Newton telescope.

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“…The unavoidable imperfections of the above physical process and the corrections that are required to mitigate the resulting limitations have been studied by all manufacturers and scientific users of CCDs (e.g., Rodricks & Venkataraman 2005;Burke et al 2005), and especially at the occasion of every space instrument embarking one (e.g., Defise et al 1997;Lo & Srour 2003;Sirianni et al 2004;Schou 2004;Penquer et al 2009;Gilard et al 2010).…”

Section: Charge-coupled Devicesmentioning

confidence: 99%

Dark signal correction for a lukecold frame-transfer CCD

Hochedez

Timmermans²,

Hauchecorne

et al. 2013

A&A

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Context. Astrophysical observations must be corrected for their imperfections of instrumental origin. When charge-coupled devices (CCDs) are used, their dark signal is one such hindrance. In their pristine state, most CCD pixels are cool, that is, they exhibit a low quasi-uniform dark current, which can be estimated and corrected for. In space, after having been hit by an energetic particle, pixels can turn hot, viz. they start delivering excessive, less predictable, dark current. The hot pixels therefore need to be flagged so that a subsequent analysis may ignore them. Aims. The image data of the PICARD-SODISM solar telescope require dark signal correction and hot pixel identification. Its E2V 42-80 CCD operates at −7.2• C and has a frame-transfer architecture. Both image and memory zones thus accumulate dark current during integration and readout time, respectively. These two components must be separated in order to estimate the dark signal for any given observation. This is the main purpose of the dark signal model presented in this paper. Methods. The dark signal time-series of every pixel was processed by the unbalanced Haar technique to timestamp when its dark signal changed significantly. In-between these instants, the two components were assumed to be constant, and a robust linear regression, with respect to integration time, provides first estimates and a quality coefficient. The latter serves to assign definitive estimates for this pixel and that period. Results. Our model is part of the SODISM Level 1 data production scheme. To confirm its reliability, we verified on dark frames that it leaves a negligible residual bias (5 e − ) and generates a small rms error (25 e − rms). We also examined the distribution of the image zone dark current. The cool pixel level is found to be 4.0 e − pxl −1 s −1 , in agreement with the predicted value. The emergence rate of hot pixels was investigated as well. It yields a threshold criterion at 50 e − pxl −1 s −1 . The growth rate is found to be on average ∼500 new hot pixels per day, that is, 4.2% of the image zone area per year. Conclusions. A new method for dark signal correction of a frame-transfer CCD operating near −10• C is described and applied. It allows making recommendations about the implementation and scientific usage of such CCDs. Moreover, aspects of the method (adaptation of the unbalanced Haar technique, dedicated robust linear regression) have a generic interest.

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Modeling of proton-induced CCD degradation in the Chandra X-ray Observatory

Cited by 24 publications

References 15 publications

A magnetic diverter for charged particle background rejection in the SIMBOL-X telescope

A magnetic diverter for charged particle background rejection in the SIMBOL-X telescope

Update on the use of Geant4 for the Simulation of low-energy protons scattering off X-ray Mirrors at grazing incidence angles

Dark signal correction for a lukecold frame-transfer CCD

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