Silicon photodiode soft X-ray detectors

Abstract

Summary form only given, as follows. Advanced fabrication techniques have produced UV/soft X-ray silicon photodiodes of uniform quality with thin (60 Angstrom) entrance windows and response times on the order of 100 picoseconds. We have assembled these advanced diodes into small individual detectors and detector arrays used on our plasma diagnostic experiments. Synchrotron X-ray and visible light calibration measurements show an essentially flat response from 10 eV to 600 eV as theoretically expected. Above 600 eV detector response increases above the theoretical calculation due to transmission through an approximately 8000 Angstrom thick SiO/sub 2/ protective layer surrounding the central 'active' area of the diode. Measurements on a number of diodes verify the manufacturer's claim of diode to diode response variation of about 5%. Pulsed soft X-ray calibrations show an increase in time response as a function of increased signal level and reduced bias voltage. Silicon photodiodes are the ideal detectors for soft X-ray measurements as they are much more stable and less variable in response than photoemissive detectors and much less costly than photoconductive diamond sensors. These characteristics coupled with the fast time response of the advanced silicon diodes make them excellent sensors for the soft X-ray diagnostics required on plasma experiments.