The effect of event shape on controiding in photon counting detectors

Kawakami, Hiroyoshi; Bone, D. A.; Fordham, J. L. A.; Michel, R.

doi:10.1016/0168-9002(94)90830-3

Cited by 22 publications

(20 citation statements)

References 4 publications

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“…The resulting photon splash on the CCD covers several neighbouring CCD pixels (with a FWHM of approximately 1.1 CCD pixels, if fitted with a Gaussian). The splash is centroided, using a 3 × 3 CCD pixel subarray to yield the position of the incoming photon to a fraction of a CCD pixel (Kawakami et al 1994). An active area of 256 × 256 CCD pixels is used, and incoming photon events are centroided to 1/8th of a CCD pixel to yield 2048 × 2048 pixels on the sky, each 0.4765 arcsec square.…”

Section: Detectormentioning

confidence: 99%

The XMM-Newton optical/UV monitor telescope

Mason

Breeveld

Much

et al. 2001

A&A

617

512

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Abstract. The XMM-OM instrument extends the spectral coverage of the XMM-Newton observatory into the ultraviolet and optical range. It provides imaging and time-resolved data on targets simultaneously with observations in the EPIC and RGS. It also has the ability to track stars in its field of view, thus providing an improved post-facto aspect solution for the spacecraft. An overview of the XMM-OM and its operation is given, together with current information on the performance of the instrument.

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Section: Detectormentioning

confidence: 99%

The XMM-Newton optical/UV monitor telescope

Mason

Breeveld

Much

et al. 2001

A&A

617

512

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“…A fibre optic taper images these scintillations on to a fast-scanning (10 MHz horizontal clock, 1.25 MHz vertical clock) frame transfer CCD camera. Captured events are recognized within the video signal by the processing electronics and centroided to 1/8 of a CCD pixel to overcome, as far as possible, resolution losses associated with the intensifier (Kawakami et al 1994;Michel, Fordham & Kawakami 1997). The CCD used is a TH7863 manufactured by Thomson CSF.…”

Section: F R E E R U N M O D E W I T H T H E M I C P H O T O N C O U mentioning

confidence: 99%

High time-resolution spectroscopic imaging using intensified CCD detectors

Fordham

Kawakami

Michel³

et al. 2000

Monthly Notices of the Royal Astronomical Society

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A B S T R A C TThe micro-channel plate intensified CCD photon counting detector developed at University College London has been upgraded to allow time-resolved spectroscopic optical data to be acquired on periodical sources such as pulsars. First observing trials have been carried out, acquiring spectroscopic data on the Crab pulsar. The detector was phase locked to the pulsar period and a temporal resolution of 41.4 ms employed. The phase locking allowed the coaddition of time slices over a large number of pulsar periods to build up quantifiable spectroscopic data when observing in a flux-limited regime.Key words: instrumentation: detectors ± methods: observational ± techniques: miscellaneous. I N T R O D U C T I O NIn most imaging applications using a CCD camera, whether a fullframe imager as normally employed in astronomy or a frame transfer device as used in video applications, the acquisition of an image can be split into two phases; the integration period and the readout period. For the integration period, the clocks connected to the imaging area of the CCD are held at constant levels to allow a photo-electron charge to be accumulated, thus building up an image on the chip. In the readout period this image is then accessed by activating the pixel clocks so that the image is transferred row by row to the readout register where the image is read out one pixel at a time. The highest rate at which frames of data can be transferred, which limits the temporal resolution available, is governed by the readout period. This is typically in the range of milliseconds/frame, for small format CCDs that employ frame transfer, to many seconds/frame for large-format full-frame imagers.If, now, the integration period is removed and the CCD clocks are allowed to operate continuously with each vertical transfer being followed by a row readout (i.e. the CCD is operating in a Freerun mode) then, for two-dimensional images, all features will be smeared out vertically as shown in Fig. 1. However, for onedimensional images which subtend a single CCD row (such as a stellar spectrum), each row will become a time slice through the input with the integration time being equal to that required to shift and read out a row. In this mode of operation there is no vertical spatial dimension to an image and the same result would be obtained with a simple linear CCD.Hence, in principle, high time-resolution spectroscopy on stellar sources can be achieved by continuous clocking. However, a problem exists. Except on very bright sources, the flux acquired per time slice will be very low and readout noise on the CCD (even at the lowest levels) will dominate. As an example, on a 10th magnitude star, the expected signal with an 80 per cent efficient CCD using a 4.2-m telescope would be ,0.06 e 2 /A Ê in a 40 ms time slice (based upon measured efficiency figures for the William Herschel Telescope ± see website www.ing.iac.es/,sjst/ isis). This leads to the conclusion that this operating mode, called Freerun mode', can only realistically be employed w...

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“…Low gain MCP operation increases the local count rate capabilities because less charges are required to deplete the pores [12]. Often, the MCP electron shower is considered to be Gaussian, which is a simplified assumption since the MCP pore bias angle renders the distribution asymmetrical and makes the event footprint elliptical instead of circular [15]. This effect can be neglected for small charge clouds and a relatively high acceleration field between the MCP backside and the imaging detector [14].…”

Section: Introductionmentioning

confidence: 99%

“…Selected, often used centroiding algorithms for sparse emission data sets, are center-of-gravity (COG) centroiding, centroiding algorithms based on analytical functions (that describe the emission cloud) or "interpolated convolution". Center-of-gravity (COG) centroiding [9,10,13,[15][16][17] is a simple and popular centroiding method. The center coordinates of a signal cluster are determined by calculating a weighted average over the signal cluster.…”

Section: Introductionmentioning

confidence: 99%