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 itsdistribution is measured by a spectrometer system consisting of a pulsedmagnet, which deviates the beam from the Transfer Line, and a 60 degreesbending magnet, which focuses the beam on a hodoscope of secondary emissionmetallic strips.

The beam from the Linac can also be directed by means of a DC magnet,in a dedicated mode which is not compatible with injection into the collider,towards a Test Beam area, mainly conceived for detector calibration. Forthis purpose, a system of absorbers, energy and phase- space scrapers canstatistically reduce the beam intensity down to a single electron per pulse.

The Linac is fully operational. The design parameters have been achievedwith both electrons and positrons.



RF frequency2856 MHz
Klystron power45 MW
Number of klystrons4
Number of SLED peak power doublers4
Number of accelerating sections15
Repetition rate50 Hz
Beam pulse width10 ns


Number of accelerating sections5
Input current from gun< 10 A
Input energy from gun120 KV
Harmonic prebuncher
Output current> 4 A
Output energy250 MeV
Output emittance< 1 mm.mrad
Energy spread10% fwhm
Beam spot radius1 mm r.m.s.


Number of accelerating sections10
Output energy550 MeV
Input energy2 < E < 14 MeV
Output current36 mA
Output emittance< 5 mm.mrad
Energy spread2% fwhm


Output energy800 MeV
Output current150 mA
Output emittance< 1mm.mrad
Energy spread1% fwhm

M.Preger29 JUN 1998