* Corresponding author. Tel.: #39-0116707317; fax: #39- 0116691104. E-mail address: vittone@to.infn.it (E. Vittone). Nuclear Instruments and Methods in Physics Research A 458 (2001) 360}364 CVD diamond microdosimeters C. Manfredotti, A. Lo Giudice, C. Ricciardi, C. Paolini, E. Massa, F. Fizzotti, E. Vittone* Experimental Physics Department, University of Torino (I), via Pietro Giuria 1, 10125 Torino, Italy INFM, Unity of Torino University, Italy Istituto di Metrologia **G.Colonnetti++, CNR, Torino, Italy Abstract CVD diamond detectors have been evaluated for use as X-ray dosimeters. The response both at radiological diagnostic and at therapeutic energies of one `detector gradea commercially available parallelepiped CVD sample has been measured and compared with the performances of a `needle shapeda CVD diamond detector grown by the hot-"lament CVD technique on a tungsten tip. All the detectors were demonstrated to be very suitable for bio-medical application: they are linear in dose rate, stable and relatively fast, with a signal-to-noise ratio higher than 1000.  2001 Elsevier Science B.V. All rights reserved. PACS: 52.75; 81.05.T; 07.85.F; 29.40.W; 87.53.b Keywords: CVD diamond; X-ray detectors; Solid-state detectors; Dosimetry 1. Introduction Diamond is an ideal material as radiation detector for bio-medical applications [1]. The at- tractiveness of diamond essentially stems from its radiation hardness, chemical stability against all the body #uids and its absolute nontoxicity. More- over, diamond is to be considered as a `tissue- equivalenta material since its atomic number (Z"6) is close to the e!ective atomic number of soft tissue (Z  "5.92 for fat and Z  "7.4 for muscle) [2]. This fact is particularly important to measure the absorbed dose in biological tissue where the energy deposited by low-energy gamma or X-rays ( (150 keV) is highly dependent on the atomic number of the material. For this reason the unit of absorbed dose for ionising radiation, the gray (Gy"J/kg), or for dose equivalent, the sievert, is approximately the same for tissue and for dia- mond. Improved diamond synthesising techniques have generated new optimism on the possibility of ap- plying diamond in radiation detection, overcoming the di$culties (high cost and poor reproducibility) which limit the widespread application of natural diamond in this "eld. In particular, the Chemical Vapour Deposition (CVD) technique has proven to be able to produce low-cost `detector-gradea dia- mond "lms suitable for application in radiation 0168-9002/01/$ - see front matter  2001 Elsevier Science B.V. All rights reserved. PII: S 0 1 6 8 - 9 0 0 2 ( 0 0 ) 0 0 8 8 2 - 2