R & D of Nondestructive beam profile monitor with residual gas (RGBPM)

It is very important to measure the profile and intensity of the high power beam in the viewpoint of the prrecise beam transport to the production target. And the possible beam loss caused by installing materials over the beam axis must be avoided in the viewpoint of radiation safety.
To solve this problem, we are developing a new type of beam monitors. The beam duct is usually kept in the vaccuum, but there is a little residual gas. When the beam passes through the duct, residual gas is ionized and makes ion pairs (electron and positive ion). The beam profile can be measured by collecting electrons or ions in the horizontal and/or vertical direction, applying electrostatic field.

Fig.1 is the photo of the first prototype of RGBPM before the installtion to the neutrino beam line in KEK 12GeV PS. Fig.2 shows the results of the first beam test. The signal from RGBPM isclearly observed in coincidence with the signal of the existing beam current monitor (SEC). This test proved the fruitful possibility of RGBPM. We will continuously do many kinds of test in order to make realistic beam monitors under the high power beam environment.

Fig.1: A photograph of the first prototype of RGBPM. There is a structure to make electrostatic field and an electron multiplier to enhance the signal.

Fig.2: The result of the first beam test. The upper signal shows the raw signal from the existing beam current monitor (SEC) and the lower one shows the signal from RGBPM. Signals can be observed in coincidence with the duration of the beam extraction.