0 Measurement of the six Dimensional Phase Space at the New GSI High Current Linac

For the characterization of the 10 mA ion beam delivered by the new High Current Linac at GSI, sophisticated , mainly non-intersepting diagnostic devices were developed. Besides the general setup of a versatile test bench, we discuss in particular bunch shape and emittance measurements. A direct time-of-flight technique with a diamond particle detector is used to observe the micro-bunch distribution with a resolution of ∼ 25 ps equals 0.3 o in phase. For the determination of the energy spread a coincidence technique is applied, using secondary electrons emitted by the ion passing through an aluminum foil 80 cm upstream of the diamond detector. The transverse emit-tance is measured within one macro pulse with a pepper-pot system equipped with a high performance CCD camera. At GSI upgraded ion sources [1] as well as a new 36 MHz RFQ-and IH-Linac designed for high current operation was commissioned in 1999 [2]. New beam diagnostic developments were necessary due to the high beam power up to 1.3 MW at an energy of 1.4 MeV/u within a macro pulse length of maximal 1 ms. A beam diagnostics bench was installed behind each Linac-structure during the step-wise commissioning, the scheme is shown in Fig.1. Non-destructive devices are used for following tasks: The total current is measured using beam transformer [3] made of Vitrovac 6065 core having a 2×10 differential secondary winding. The resolution is 100 nA at a bandwidth of 100 kHz. Due to a feedback circuit the droop is less than 1 % for 5 ms macro-pulses. The beam energy is determined by a time-of-flight technique using two 50 Ω matched capacitive pickups [4] with 1 GHz bandwidth, separated by 2 m. A precision of ∆W/W = 0.1 % is achieved. The beam position is monitored by digitizing the power of the 6 th harmonics of the rf frequency (216 MHz) of the 4 segments of these pickups. The beam profile is determined by a residual gas monitor [4], where residual gas ions are detected on a 23 strip printed board. For typical beam parameters no significant broadening of the profiles due to space charge influence is expected. For lower current or shorter macro pulses conventional profile grids are used. The instruments are now installed behind the last IH2 cavity as well as behind the gas stripper. In the following Figure 1: Scheme of the test bench as arranged for the commissioning of the RFQ. …