NEUTRON DAMAGE OF CHEMICAL-VAPOR-DEPOSITION DIAMOND

Many of the components of particle detectors for the next generation o f high energy experiments need to be extremely radiation-hard ii they are to continue to function for more than a few months. For example, i n the first few year's operation of the large hadron collider, we expe ct about 10(13) neutrons cm(-2) year(-1) 1 cm from the beam pipe, with other particles causing about ten times as much additional damage. Di amond is being considered as both a detector material and perhaps as a structural component. We report on tests of chemical vapour depositio n diamond films irradiated by 6 x 10(14) neutrons cm(-2) of energy bel ow 10 keV, plus (2.0 +/- 0.5) x 10(14) neutrons cm(-2) of energy above 10 keV peaking at about 1 MeV. The diamonds were metallized with tita nium-gold contacts-strips on the front and a continuous electrode on t he back. The leakage current (already extremely small) decreased by fa ctors of about 50 as a result of the irradiation, both measured betwee n adjacent strips and through the thickness of the samples. The detect ion efficiency of charged particles improved by 30-40% after irradiati on. In addition, natural diamonds irradiated by 4 x 10(14) neutrons cm (-2) showed very little optical absorption in the GR1 and ND1 bands (n eutral and negative vacancy) corresponding to a concentration of vacan cies of 4(+/-2) x 10(14) cm(-3).