A FAST AND FLEXIBLE MULTICHANNEL ELECTRON DETECTOR WITH PARALLEL READOUT FOR PHOTOELECTRON-SPECTROSCOPY

To satisfy end user requirements for higher throughput and reliability in photoelectron spectroscopy, a new multichannel electron detector w ith discrete electronics has been designed and commissioned at Daresbu ry Laboratory. Count rate performance has been enhanced by the use of low resistance microchannel plates which amplify the electron pulses i ncident on the anode array. The low resistance microchannel plates are linear to 2.5 x 10(4) s(-1)mm(-2) for a bias voltage of 900 V per pla te, providing more than an order of magnitude improvement in count rat e performance over high resistance microchannel plates, microchannel p late outgassing in the ultra-high vacuum environment limits the scale of this improvement. A novel anode design maximizes the collection eff iciency, while minimising crosstalk between channels (< 0.6% after dis crimination) and provides up to 40 parallel channels on a 1 mm pitch. The collection efficiency is increased from 50% to 70% (for the presen t geometry) by applying a 50 V bias between the guard rail and electro des on the anode. Each data collection channel comprises a fast curren t amplifier and discriminator, capable of a throughput of 2.5 x 10(7) s(-1), and a 24 bit scaler. The integral non-linearity for flat-field illumination is better than 10% with no correction. The fast multichan nel detection system gives a throughput enhancement of 10-20 on single -channel detection systems. It has also proved to be significantly bet ter than previous multichannel detection systems with discrete electro nics due to its high throughput, modular design and flexible structure .