The 14th Symposium on Accelerator Science and Technology, Tsukuba, Japan, November 2003

A 400m-LONG SUPERCONDUCTING RF LINAC CRYOSTAT DESIGNFOR AN ERL LIGHT SOURCEEisuke. J. Minehara, FEL Laboratory at Tokai, JAERI, 2-4 Tokai, Ibaraki, 319-1195 JAPAN
Abstract
A so-called 4th generation synchrotron radiation
light source for a large-scale user facility like the 3rdones has been recently discussed to realize using asuperconducting RF linac-based FEL [1] or an energy
recovery linac (ERL) light source [2]. In order to realizeboth of them, we need very large number of lowtemperature cryostats to run them routinely andefficiently. A 400m-long superconducting RF linac
cryostat is conceptually designed here and discussed tooptimize major operational characteristics of theadvanced low-temperature cryostat for an ERL lightsource near future.

Cryostat Heat Load
10000

cavity No
beampipe No

1000

HePipe No
RFCNop80

100

Total Heatload p80
RFCNop20

10

CRYOSTAT CONSIDERATION FOR
INDUSTRIAL ERL LIGHT SOURCES
In order to realize quickly an industrial energy
recovery linac (ERL) light source, a 400m-longsuperconducting RF linac cryostat is conceptuallydesigned and discussed to optimize major operational
characteristics of the advanced low-temperature cryostat
for an ERL light source near future. A low temperaturecryostat for superconducting RF linacs and othersuperconducting devices should be designed and made tominimize its heat invasion through the heat bridges
between the room and low temperature parts. The
cryostat also should be designed and made to minimize
total number of the heat cycles for the rest of its life after
the initial test. We can expect that the total number ofthe heat bridges is roughly proportional to the number ofthe cryostat, and a life interval between two contiguous
cryostat malfunctions inversely proportional to thenumber of the heat cycles. Therefore, if we can design
and make a single and long cryostat to realize theoperation less than a half cycle for the rest of its life, wecan run our cryostat for a very longer interval than tensof years and with minimum electricity. In addition tothem, we plan to summarize the JAERI ERL FEL zeroboil off cryostat design, its operational characteristics,
and non-stop operation records over these 12 years andother cryostat related activities in the poster presentation.
Each cryostat usually has one or two liquid He
feeding ports, and two beam pipes, several RF main andhigher mode couplers. Here we assumed that the ERL
has 800 cavities, 400m accelerating length, average
acceleration gradient of 10-15MeV/m, and total electronenergy 4-6GeV. Horizontal axis is number of cavities
installed in each cryostat, vertical one total static heatload. Minimal static heat load will be realized if we canTotal Heatload p20
RFCNop211

101001000

Total Heatload p2

No. Crostat

Figure, Static Cryostat Heat Load and No. of Cryostat.

choose a single and longest cryostat, and the maximum
load the shortest cryostat. Because we intend to use thecryostat for the ERL, RF power for the main accelerator
linac will be recovered and the power supply will feed alarge number of cavities. In the figure, there are 3 casesof cavity number fed by one RF port, i.e., 1, 4, and 40,
and "Total Heat Loadp80", "Total Heat Loadp20", and"Total Heat Loadp2" indicate them respectively.. Themaximum heat load became 3.2kW at low temperature,and the minimum 24W.
Heat shield of the long and single cryostat will becooled down by using integrated refrigerators system like
existing JAERI zero-boil off cryostat system [3].

REFERENCES[1] TESLA Technical Design Report, DESY 2001-011,
March 2001.
[2] I.V.Bazarov et al., ”The energy recovery linac (ERL)
as a driver for X-ray.
[3] E.J.Minehara et al., pp159-161, in the proceedings ofParticle Accelerator Conference, 1995, Dallas.
E.J.Minehara et al., Free Electron Laser Challenge2(SPIE) Vol.3614, pp.62-71, 1999.
E.J.Minehara et al., Nucl. Instrum. Methods Phys.
Res. Sect.A445, 183 (2000).