LINAC

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 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.

LINAC PARAMETERS

GENERAL

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

HIGH CURRENT ELECTRON LINAC

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.

POSITRON LINAC MODE

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

HIGH ENERGY ELECTRON LINAC MODE

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