Irradiation control of the 'Spiral' target by measuring the ion beam intensity via a fast current transformer

In order to obtain a more precise control on the irradiation of the targets of the 'SPIRAL' installation, a new criterion of safety must be respected. To control this latter, an assurance quality system has been put in operation and more specifically a new device has been set up in order to measure the ion beam intensity and to calculate the number of particles per second. This value can then be integrated over time. This device consists of two Fast Current Transformers integrated in a mechanical unit placed in a vacuum chamber. These sensors reproduce the image of the pulsed beam at 10 MHz and we take from the amplified signal of each sensor, the amplitude of the second harmonic. Each one of these amplitudes is detected by a Lock-in Amplifier, which is acquired via a real time industrial controller. The intensity is calculated by the Fourier series relation between the amplitude of the second harmonic and the average intensity. This equipment can be remotely tested by integrating a test turn on the sensors. They are redundant. The accuracy of measurement is estimated taking into account the variation of the beam, of the environment and of the installation. (authors)