Catalogues - x-ray-counting-system

Catalogue X-ray counting system

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X-ray counting system DM0011

Sens-Tech

SENSOR TECHNOLOGIES

1 description

The DM0011 is a wide dynamic range, X-ray counting system. X-rays up to 100 keV are detected using a scintillator coupled to a photomultiplier and signal processing electronics to provide a tTl output.

The detector uses a window discriminator to detect X-rays within a selected energy band. The width and threshold (lower limit) of the window and the HV of the photomultiplier can be set by the user with the DM0011CONTROL. A schematic of the window discriminator and read out is shown in section 5.

Fast count rates are achieved by using a YAP(Ce) scintillator, selected for its very fast (30 ns) decay time, and high speed electronics, designed to minimise dead-time. A plot of indicated counts against true counts is shown in section 6.

As well as counting X-rays in a set energy band, the unit can be used to generate an energy spectrum by using a narrow (energy) window and progressively increasing the lower threshold. This feature is also used to calibrate the detector, using gamma and X-ray sources of known energy. A sample energy spectrum is shown in section 7.

5 window discriminator schematic

Only pulses falling in the window, between the lower level (LLD) and upper level (ULD) are detected.

2 applications

The unit is designed to count X-rays in laboratory or production equipment and in synchrotron radiation experiments.

shaping __|\__amplifier a

logic and O/P driver

YAP(Ce)

«- • uin I—

pmt

X-ray

* LLD


ULD LLD 0 V output	signal < LLD	LLD < signal < ULD	signal > ULD A
		a	A
		/\,
		n

10 MHz count capability 0.15 Hz background count adjustable window discriminator adjustable sensitivity compact assembly

operates from a single low voltage supply TTL output

37 ns

4 specification

6 indicated counts vs true counts

detection range

window discriminator lower (min) upper (max)

window width

count rate

actual counts indicated counts

scintillator

background counts

supply voltage

5 keV to 100 keV

0.100 V

3.00 V

variable,3Vmax

10 MHz max (note1) 5 MHz max

YAP(Ce) 21.8mmdia

0.15 Hz (note 2)

+4.75 V min +5.25 V max ripple < 100 mV pk-pk 60 mAmaxat 1 MHz

count rate

The true count rate N can be calculated from the measured value n by iteration, using the expression n = Ne^- ^x, where x is the dead-time. This may be approximated for nx <<1 to N = n/(1-nx).

10 9 8 7 6 5 4 3 2

1 0

supply current

note1: afterdead-timecorrection

note 2: 0.15 Hz maximum (8 keV to 50 keV), unit shielded with 6 mm of lead

456

789

— n = Nexp(-Nx)

N MHz

- linear response