A. P o r t e r , University of Manchester LONDON P rin te d a n d P u b lish e d fo r th e R o y a l S ociety

Diamond substrates supporting an internal array of conductive graphitic wires inscribed by a femtosecond pulse laser, are useful for the detection of ionising radiation in a range of applications. Various parameters involved in the laser fabrication process were investigated in this paper to understand their impact on the electrical properties of the wires. The study revealed an effect, whereby the wires exhibit insulating behaviour until a barrier potential is overcome. When high enough voltages are applied, the wires display ohmic behaviour. The magnitude of the barrier potential, which in some cases exceeds 300 V, is shown to be strongly dependent on the laser fabrication parameters. Through process optimisation, the potential barrier may be minimised and effectively removed, coinciding with reduced values of the wire resistance.

1-I n t r o d u c t io nIn a previous paper (Callender, H artree and Porter 1936),* three of the present authors have given a theoretical study of the effect of a time-lag on a general class of control systems.I t was supposed th a t some physical quantity (such as temperature), subject to random disturbances, was to be kept as nearly constant as possible by the operation of certain controlling gear, this operation being related in a definite way to the behaviour of the physical quantity to be controlled, and further th a t there was a time-lag between such operation * T his p a p e r (vide R eferences) will be q u o te d as I. on May 12, 2018 http://rspa.royalsocietypublishing.org/ Downloaded from

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Diamond is used as detector material in high energy physics experiments due to its inherent radiation tolerance. The RD42 collaboration has measured the radiation tolerance of chemical vapour deposition (CVD) diamond against proton, pion, and neutron irradiation. Results of this study are summarized in this article. The radiation tolerance of diamond detectors can be further enhanced by using a 3D electrode geometry. We present preliminary results of a poly-crystalline CVD (pCVD) diamond detector with a 3D electrode geometry after irradiation and compare to planar devices of roughly the same thickness.

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When electrons strike a surface with sufficient velocity, secondary electrons may be emitted by it, some or all of which may be collected by a suitable electrode having a higher potential than the emitting surface. (“Secondary electrons” are here taken to mean all electrons which leave the surface, whether reflected, rediffused, or actually emitted by the surface.) In the work to be described, a triode is considered, in which the anode receives electrons from the cathode, and emits secondary electrons which are collected by the grid, which is maintained at a higher positive potential than the anode. In the experimental work, a triode with an axially symmetrical configuration of electrodes was used, and such a triode will be considered in the theoretical work.