JLC ATF Group Home Page

Welcome to ATF Group Home Page

17 May 1995

The JLC ATF group is charged of R&D aiming at a possible design of the JLC Accelerator with the center-of-mass energy of 300-500 GeV. Here in this home page we introduce you to activities of the ATF group. The home page is still incomplete but to be enriched gradually. Any comments or suggestions are welcome and to be directed to takeda@jlcux1.kek.jp

What's New?
ATF Group Member
Current Activities
1.54 GeV ATF Injector Linac
Getting Started
ATF Group Calendar
Library

What's New?

Introduction of the ATF Group

The current members of the ATF group include:

Current Activities

Introduction of the 1.54 GeV ATF Injector Linac

It is essential to produce a low emittance beam with a reasonable damping time, since the spot size is limited by the emittance of the beam. To confirm experimentally its feasibility, we are now constructing ATF (Accelerator Test Facility) at KEK. The ATF consists of two major components: a 1.54 GeV S-band injection linac and a damping ring. The construction of the ATF is one of the most important ingredients of the second 3-yesrs R&D program emphasizing the practical aspects to build an e+e­ linear collider facility. The ATF project is expected to achieve its goal in next two years.


The 1.54 GeV S-band Linac
The injector consists of a conventional thermionic gun, a 357 MHz subharmonic buncher, and a 3 m long S-band buncher structure which is followed by 3 m long constant gradient traveling wave structures. The overall length of the linac is 75 m in which 18 structures, focusing magnets, and various monitors are placed.


The 100 MW S-band Klystron
Two structures are driven by one 100 MW klystron which can produce 4.5 micro-sec long RF pulse.


The 400 MW SLED Cavity
A newly developed SLED cavity compresses the output pulse from the klystron and produces a 1 micro-sec long RF pulse with a peak power of 400 MW. The compressed pulse is divided into two and fed to each structure providing an average acceleration gradient of 40 MeV/m with beam loading. In the present design two of the 18 structures are operated with slightly different frequencies, which compensates the energy differences and keeps the bunch-to-bunch energy spread to about 0.15%. The invariant emittance at the entrance of the regular section is expected to be 3 x 10**-4 rad.m. The emittance blow-up in the injector is required to be less than 50 % in order to match the ring acceptance. The lattice was designed to meet this requirement with a minimum space factor. Two triplets are only placed at the upstream end and doublets are limited to the first half of the linac. The remaining half of the linac simply consists of singlets. The alignment tolerance is 200 microns for both structures and quads, which is expected to be achievable using a wire alignment method.


The Wire Alignment System
Needless to say, it is essential that a multi-bunch beam can be extracted with sufficient intensity from the thermionic gun. To this end we have been developing a grid driver which consists of a fast ECL circuit and an RF power amplifier.


The Electron Source
Recently the thermionic electron source is succeeded in producing 20 buncheswith 2.8 nsec bunch spacing. The intensity of each bunch was measured to be 3 x 10**10 particles, which is required for the damping ring.


The Choke Mode Cavity
The choke mode cavity damps the higher order modes generaed by the bunch-cavity intaraction. The multi-bunch beam has been accelerated by the accelerating gradient of 52 MeV/m in the choke mode cavity.

Getting Started

Mailing List

ATF group Calendar

Library

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