| Paper | Title | Page |
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| TUPP056 | High Current Proton Beam Operation at GSI UNILAC | 550 |
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| A significant part of the experimental program at FAIR is dedicated to pbar physics requiring a high number of cooled pbars per hour. The primary proton beam has to be provided by a 70 MeV proton linac followed by two synchrotrons. The new FAIR Proton LINAC will deliver a pulsed proton beam of up to 35 mA of 36 μs duration at a repetition rate of 4 Hz. The current GSI heavy ion linac (UNILAC) is able to deliver world record uranium beam intensities for injection into the synchrotrons, but it is not dedicated for FAIR relevant proton beam operation. In an advanced machine investigation program it could be shown, that the UNILAC is able to provide for sufficient high intensities of CH3-beam, cracked (and stripped) in a supersonic nitrogen gas jet into protons and carbon ions. This advanced operational approach results in up to 2 mA of proton intensity at a maximum beam energy of 20 MeV, 100 μs pulse duration and a rep. rate of 4 Hz. Recent linac beam measurements will be presented, showing that the UNILAC is able to serve as a proton FAIR injector for the first time, while the performance is limited to 17% of the FAIR requirements. | ||
| TUPP057 | In Situ Measurement of Mechanical Vibrations of a 4-Rod RFQ at GSI | 553 |
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A new 4-rod CW Radio Frequency Quadrupole was commissioned at the high charge state injector HLI at the UNILAC in 2009. It is in operation since 2010*. At high rf amplitudes strong modulations of the rf reflection emerge, with a modulation frequency of approximately 500 Hz. They are attributed to mechanical oscillations of the rods, excited by the rf pulse. The high fraction of reflected rf power severely limits the pulse length and rf amplitude achievable. As these modulations could only be seen during the rf pulse by means of rf measurements, a direct observation of the mechanical vibrations was desirable. Such measurements have been conducted using a commercial laser vibrometer, allowing for the investigation of the mechanical behavior of the RFQ independent of the presence of rf power. After a short introduction of the method, the results will be presented and compared with rf measurements and simulations.
*: P. Gerhard et al., “Experience with a 4–Rod CW RFQ”, LINAC’12, Sept. 2012, Tel Aviv, THPB035 |
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| TUPP059 | Advanced Beam Matching to a High Current RFQ | 559 |
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| The High Current Injector (HSI) of the heavy ion linac UNILAC at GSI comprises the transport lines, the RFQ and two DTL tanks. Beam matching to the RFQ acceptance with a magnetic quadrupole quartet has been worked out manually during commissioning and operation of the machine. Due to a strong overlapping of the field from neighboring quadrupole lenses, a standard optics calculation does not provide for the required reliability. Advanced beam dynamics simulations have been done with the macroparticle code DYNAMION. The superposition of the measured magnetic fields of each quadrupole was taken into account. The quadrupole settings were optimized using the Monte-Carlo method. Two solutions have been found in accordance with the general theory of particle optics. Beam dynamics simulations with new quadrupole settings show an increased particle transmission through the RFQ. The results of numerical study have been confirmed during experimental campaigns. An improved performance of the whole HSI has been demonstrated. The proposed algorithm and a comparison of the measured data with result of simulations are presented. | ||