IntroductionThis work describes the development of a new method for recording radiation exposure by using a passive dosimeter based on a Floating Gate CMOS sensor.The floating Gate sensors based on the MOS structure discharge allow the construction of compact and cost-efficient dosimeters, realized in VLSI CMOS technology, for use in integration mode in various applications, in particular in radiotherapy. MethodsA monolithic rad-hard dosimeter has been designed starting from a standard six metal levels CMOS technology with lithography at 180nm. The radiation sensor (C-sensor) is based on a non-volatile memory cell with floating-gate which, once loaded, can provide a measure of the absorbed radiation on the basis of its threshold discharge. Since the memory cell is mainly a transistor the greater is the current flowing into the channel the greater is the dose of radiation received by the sensor. The output current of the transistor is processed by a current-voltage converter (IV converter) and interfaced to an analog-digital Flash converter (ADC) with a resolution of 5 bits. To ensure the re-use of the device both the current-to-voltage converter and the ADC have been designed to be resilient to radiation (rad-hard) to avoid a degradation of the internal circuitry that can affect the measure of the absorbed dose.ResultsTen dosimeter samples have been designed, integrated and tested under gamma irradiation at the IGS3 gamma-ray irradiator of DEIM Department of Palermo University to verify their performances. Dosimeters have been irradiated with a dose-rate of 1.44 Gy/min (Si) and in a dose range between 3 and 10 Gy(Si) and a linear relation between dose and response has been detected. Following the reading the dosimeters were reprogrammed and irradiated again to verify their re-use.ConclusionsThe results confirm that, in this first version, the dosimeter is reprogrammable and able to detect a dose up to 10 Gy (Si) with temperatures that can go from 0 to 85°C.
|Numero di pagine||1|
|Stato di pubblicazione||Published - 2019|