Fast wire per wire X-ray data acquisition system for time-resolved small angle scattering experiments

Most of the X-ray multi-wire gas detectors used at the EMBL Hamburg outstat ion for time-resolved studies of biological samples are readout, using the delay line method. The main disadvantage of such readout systems is their e vent rate limitation introduced by the delay line and the required time to digital conversion step. They also lack the possibility to deal with multip le events. To overcome these limitations, a new approach for the complete r eadout system was introduced. The new linear detection system is based on t he wire per wire approach where each individual wire is associated to a pre amplifier I discriminator / counter electronics channel. High-density, fron t-end electronics were designed around a fast current sensitive preamplifie r. An eight-channel board was designed to include the preamplifiers-discrim inators and the differential ECL drivers output stages. The detector front- end consists of 25 boards directly mounted inside the detector assembly. To achieve a time framing resolution as short as 10 mu S very fast histogramm ing is required. The only way to implement this for a high number of channe ls (200 in our case) is by using a distributed system. The digital part of the system consists of a crate controller, up to 16 acquisition boards (cap able of handling fast histogramming for up to 32-channels each) and an opti cal-link board (based on the Cypress 'Hot-Link' chip set). Both the crate c ontroller and the acquisition boards are based on a standard RISC microcont roller (IDT R3081) plug-in board. At present, a dedicated CAMAC module whic h we developed is used to interface the digital front-end acquisition crate to the host via the optical link.