Proton Linac for FAIR

The antiproton physics program of the proposed International Accelerator Facility at Darmstadt is based on a rate of 7·1010 cooled antiprotons per hour. To provide the primary proton intensities a proton linac is planned, which will be operated independently from the existing UNILAC for heavy ions. The proposed linac comprises a proton source, a RFQ, and a DTL. Its operation frequency of 352 MHz allows for an efficient acceleration to up to 70 MeV using normal conducting Crossed-bar H-cavities. These CH-cavities show high shunt impedances as known from IH-structures, but allow for much higher relative particle velocities of up to 50%. The beam pulses with a length of at least 25 µs, a current of 70 mA, and total normalized transverse emittances of 2.8 µm will allow to fill the existing synchrotron SIS within one multi-turninjection up to its space charge limit of 7·1012 protons. The maximum SIS ramping rate limits the applied proton linac repetition rate to 4 Hz. This paper gives an overview of the proposed proton linac. The status of the design including beam dynamic studies will be reported. We acknowledge the support of the European Community-Research Infrastructure Activity under the FP6 "Structuring the European Research Area" programme (CARE, contract number RII3-CT-2003-506395).

Beam energy

70 MeV

Beam current

70 mA

Protons / pulse


Beam pulse length

36 µs

Repetition rate

4 Hz

Rf frequency

325.224 MHz

Tot. tr. emit (norm.)

2.8 µm

Tot. mom. spread

± 10-3

Linac length

30 m