The DAFNE Linac during installation in Frascati.


The heart of the DAFNE injection system is a ~60 m long Linac built on the basis of a turn-keycontract. It is an S-band accelerator (2.865 GHz) driven by four 45 MWklystrons each followed by a SLED peak power doubling system. It delivers10 ns pulses at a repetition rate of 50 Hz. A quadrupole FODO focusingsystem is distributed along the entire structure.

A triode gun delivers up to 10 A electrons at 120 KV. The beam is thenaccelerated at 250 MeV by five 3 m long accelerating sections up to a removabletarget, where it is focused by a quadrupole system to a 1 mm radius spotto produce positrons with an efficiency of ~0.9%. The positrons are collectedby a high field pulsed magnetic lens, separated from the electrons by meansof a “chicane” of dipoles, and then accelerated up to a maximumenergy of 550 MeV by 10 accelerating sections. The expected positron currentduring the pulse is 36 mA within ±1% energy spread and 5 mm.mrademittance.

In the electron mode the converter is removed from the beam and theelectrons are accelerated through the whole structure up to a maximum energyof 800 MeV. The pulse current is 150 mA within ±0.5% energy spreadand 1 mm.mrad emittance.


The DAFNE Linac spectrometer magnet.


The average energy of the accelerated particles and the width of its distribution is measured by a spectrometer system consisting of a pulsed magnet, which deviates the beam from the Transfer Line, and a 60 degrees bending magnet, which focuses the beam on a hodoscope of secondary emission metallic strips.

The beam from the Linac can also be directed towards a Test Beam area BTF , mainly conceived for detector calibration purposes.

The design parameters, achieved with both electrons and positrons, are listed below.



RF frequency 2856 MHz
Klystron power 45 MW
Number of klystrons 4
Number of SLED peak power doublers 4
Number of accelerating sections 15
Repetition rate 50 Hz
Beam pulse width 10 ns


Number of accelerating sections 5
Input current from gun < 10 A
Input energy from gun 120 KV
Harmonic prebuncher
Output current > 4 A
Output energy 250 MeV
Output emittance < 1 mm.mrad
Energy spread 10% fwhm
Beam spot radius 1 mm r.m.s.


Number of accelerating sections 10
Output energy 550 MeV
Input energy 2 < E < 14 MeV
Output current 36 mA
Output emittance < 5 mm.mrad
Energy spread 2% fwhm


Output energy 800 MeV
Output current 150 mA
Output emittance < 1mm.mrad
Energy spread 1% fwhm