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Large dynamic range small-angle diffractometer D22

Small-angle scattering is a technique that measures the deviation to small angles (much less than one degree to several degrees) of an X-ray or neutron beam due to structures of small size in the sample. “Small” means dimensions of a few tenths to about 100 nanometres, such as clusters in alloys, polymers, or biological macromolecules.

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Fast Detector

Electronics

In order to exploit the performances of the PS counters, a new electronics and acquisition chain   has been designed; it includes a fast pre-amplifier, a base-line restorer, and a gaussian filter, all three stages mounted on one single printed circuit board. The analog signal, proportional to the charge, is sent to the 8 channels Digital Position Measurement card (DPM-8) by mean of a line driver; a multiplexing card (MED32) derandomizes the data and interconnect 4 DPM8 cards with the VME acquisition system. The whole electronics system has been commissioned on the new detector working on the D2B high resolution powder diffractometer, and on several prototypes of detectors.

Decoupling card

developped by : Institut Laue Langevin

This card is mounted in the rear of the detector frame in the air-tight electronics vessel. It contains 32 capacitors (68 nF). The connection between one detector (in vacuum) and one capacitor (in air) is provided by a conductive wire located inside a flexible tube. This tube is pluged on the ceramic endcape of the tube on one side, and to the electronics vessel on the other side.

Pre-amplifier, amplifier, base line restorer, gaussian filter

developped by : Institut Laue LangevinThe D22 detector will be equiped with the PAD02 IN version 0 manufactured by OSE Obiou Société d'Electronique

Time constant: 1.4 microseconds
Gain 3 V/pC

Analogic Mother Board

Manufactured by : Institut Laue Langevin

This card is equiped with 32 PAD02 circuits, and line driver

Position Calculation card

The DPM-8' developped by the Institut Laue Langevin converts the 2 signals of 8 PS counter tubes into a 8 bits position address. The pulse height of each signal is converted with a fast 12 bits ADC at a time corresponding to the maximum of the sum of the 2 signals of each tube. A pre-programmed EPROM converts these 2 informations for each event into the neutron position along the tube. Non linearities and digitization errors are corrected on-line. The position calibration and rebinning is performed off-line after the end of an acquisition.

MED-32

Manufactured by : Institut Laue Langevin
    
This card Multiplexes the data of 4 DPM-8 cards to allow a fast communication with the acquisition system, either VME or PC ("Fast/Canberra"). It reads out 32 PS counter tubes

Low voltage power supply

pm12 BTL version 1.0 supplied by Synergie Concept
+12 V/5 A and -12 V/5 A
comment : linear mode with analogic buffers +/-12v

Low voltage power supply

ZUP 10-40 BTD version 1.0 supplied by Nemic-Lambda (via Invensys)
0-10 V/40 A
comment : switch mode

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