The 11th Symposium on Accelerator Science and Technology, Harima Science Garden City, 1997

Present Status of AURORA-2DToshitada HORI
Laboratory for Quantum Equipment Technology, Sumitomo Heavy Industries, Ltd.
1-1 Yato-machi 2-chome, Tanashi, Tokyo 188 JAPANrings that succeeded in beam handling under the existence ofa superconducting wiggler.

Abstract
A new racetrack type compact SR ring AURORA-2 wasfor soft X-ray source. The bending magnets
achieved 2.7 Tesla to keep the ring small without
superconducting technology.
There are two versions,
AURORA-2S and AURORA-2D, and two rings have alreadybeen constructed. One was assembled as AURORA-2D andth~ performance tests with and without a superconducting'":'ggler were successfully completed.
The ring wasdisassembled then, and now being remodeled to AURORA2S designed for industrial use. The other is AURORA-2D
delivered to Hiroshima University with undulators and calledHiSOR.
des~gned

1 Introduction
Since 1986 we have been developing a compact SR ring
AURORA. The main target of the small ring was forindustrial use, especially for X-ray ·lithography. The firstversion AURORA is unique because of its injection methodusing half-integer resonance, which enables the ring to betruely circular, the ultimate shape of compactness. AURORA
is the only circular ring in the world using superconducting
technology by which 3.8 Tesla bending field is generated.
After the completion of development and performance tests,
the ring was transferred from our Tanashi Lab. toRitsumeikan University in 1995 [1].
. In 1994, we began to design an advanced compact ring
w1th the new concept not relying on superconducting
technology but adopting normal conducting magnet with anoble idea which enables us to use such the high magnetic
field as c.omparable to superconducting's [2]. The design has
two verswns. One design, optimized for X-ray lithography,
made the rin? as compact as possible, which has a S.ingle
quadurupole m each straight section, thus called AURORA2S. The other made the ring acceptable insertion devices on
the sacrifice of compactness, which has two quadrupole.Qoublets in each straight section, thus called AURORA-2D.
In Fig.l showing layout of AURORA-2D, the distance
between two 180° bending magnets is 7m and a part of thestraight section, actually 3m is reserved for insertion devices.
Prior to AURORA-2S~s achievement tests which isessential for our development, we began AURORA-2D's test
first after finishing the assembly in March 1997. After thesuccessful acceleration of AURORA-2D, we immediately
started the same tuning on HiSOR in Hiroshima University[3]. Soon HiSOR also acquired the sufficient stored current.
After the satisfactory results of AURORA-2D, we started
installation of the 7T superconducting wiggler in July, andbegan the wiggler test intensively from mid August. Fig.2 isan overall view of AURORA-2D taken after the installation.
After two weeks testing, we again succeeded in operation
with 7T wiggler. This is the first case of small racetrack SR

2 Design Features
The most outstanding feature of AURORA-2 lies in thedesign of 2.7T normal conducting bending magnet.
However, AURORA-2 takes over many advantages ofsuperconducting AURORA, using the 150MeV racetrack
microtron as the jnjector [4], cryopanels having high vacuum
pumping speed in the vacuum chamber of the bending
magnets, self-shielding function especially for AURORA-2S,etc. Another unique feature is in the control system. On thecontrary to other control systems, we built simple but
flexible, and economical system. It consists of one server andfour PC's connected together by LAN. Signals aretransmitted on GPIB to all equipments as shown in Fig.3.
Under this system, obsolete hardwares are easily replaced.
More precise features of both AURORA-2S and -2D arepresented in Reference [2]. The parameters related to thewiggler are listed in Tabel 1. Beam simulation results ofAURORA-2D in the presence of wiggler, single and double,
are described in References [5], [6].

3 Results of Beam Tests
The test started to transport the beam from the !SOMeV
microtron to AURORA-2D. After conditions of the injector
and BT line were optimized, beam acceleration test started inearly April. It took just one week to find the proper ramping
pattern keeping the synchronization between both thebending and quadrupole fields. What necessary while
acceleration is to take into account the eddy current effectind~ced in the massive bending magnets made of solid iron,which causes some delay in the rising of magnetic field.
Fig.4-a) shows the effect of eddy current which increases inproportion to the exciting speed di/dt. To keep the operation
ponit stable, we need to compensate the drift of the point due
to the above effect. Thus, we introduced time difference
between the ramping pattern of bending and twoquadrupoles. We chose the exciting speed 6A/sec for the
ramping of bending magnet from l03A to 833A. It takes two
minutes to accelerate the beam from 150MeV to 700MeV.
After we investigated the behavior of the ring,commissioning of HiSOR started.
We succeeded inaccumulating 700MeV beam in both AURORA-2D andHiSOR within a month. In principle the behaviors of tworings were about the same and we did not find any
inconvenience derived from individuality of two rings.

3.1 Beam Test of AURORA-2D
The operation of AURORA-2D without wiggler started inApril and stopped in July in order to install thesuperconducting wiggler. As the operation was interrupted-534-

The lith Symposium on Accelerator Science and Technology, Harima Science Garden City, 1997

once in a while, vacuum improvement work for instance, thenet testing period was limited to forty days in total. Within
this short period, we recorded 318mA stored current at700MeV, starting from 384mA of injected beam. Theacceleration efficiency was 83% in this case. The maximum
injected current at 150MeV recorded 424mA. The life time
was limited around 30min at lOOmA because of poor
vacuum. We did not have time to see the aging effect.
On the contrary to AURORA-2D, HiSOR has been
keeping in operation since May and the evidence of aging
effect seems guradually coming out. Recently they got 1.5hrslife time at l OOmA after the operation only 12A · Hr ofintegrated dose. They are entering the 10·9 Torr vacuum levelat IOOmA. We could expect the improvement of HiSOR'sperformance in accordance with the advancing of aging
process in the vacuum chamber.
3.2 Beam Test with 7 Tesla Wiggler
The main pole of the wiggler is kept at 1.5T while injectionand excited to 7T while accumulation. It takes 5.5min. toaccelerate the beam from 150MeV to 700MeV. As shown inFig.4-b), the ramping pattern of the wiggler was made withconstant di/dt of the exciting current, actually increased from
14A to 214A by di/dt=0.6 A/sec. It is equivalent to excite thebending field as dB/dt. While ramping, the saturation effectof the bending magnet appears in the last quarter. Therefore,
we must increase the exciting current of the bending magnet
steeply in the final quarter. If we apply this ramping pattern
to the ring without wiggler, we can shorten the acceleration
period about 25%, from 2min. to 1.5min.
The test was carried out under the poor vacuum condition,
I X 1o-s Torr base pressure in the straight section, for we did
not have time to wait until good vacuum. The obtained
results were as follows; max. injected 150MeV current= 116mA, max. accumulated current = 19mA, and typicalacceleration efficiency =32% starting from 56mA and 18mA
remained. This low efficiency is mainly derived from poor
vacuum 5x I o- 7 Torr while acceleration. When the starting
current was reduced to 18.6mA, then we obtained 61%
efficiency with 11.4mA remaining.
4 Future Plan

primary aim to confirm the performance of the compact ring
optimized for X-ray lithography. The configuration of newcompact SR ring is shown in Fig. 5, where shielding walls
covering the whole machine for the purpose of self radiation
protection are illustrated. Next beam test using AURORA2S is planned to start within this year. The milestone 6f thecoming beam test is to achieve the 500mA stored current, andplanned to increase up to 1000mA eventually.
5 Conclusion
It is proved that the compact SR ring AURORA-2D can
co-operate with superconducting wiggler. It is inevitable fora racetrack ring such as AURORA-2D to have somedispersion in the straight section, but not harmful when thevalue is small. Low energy injection scheme which iscommon for compact rings is not favorable for a wiggler
because of its dynamic field increasing while acceleration,
but this condition is also manageable. We experimentallyconfirmed that in spite of some difficulties small SR rings arecapable of installing a superconducting wiggler.
References[1] "Rits SR Center Activity Report 1996", Ritsumeikan
Univ. (1997) pp.3-7.
[2] T. Hori, et al., "AURORA-2: Compact Advanced SR
Ring as an X-ray Source", 4th Int'l Conf. on SR Sourcesand 2nd Asian Forum on SR, Kyongju, Korea (1995)
pp.l48-158.
[3] K. Yoshida, et al., "Compact Synchrotron Light SourceofHSRC", Submitted for Synch. Radiation Instrum. '97,Himeji, Japan (1997).
[4] T.Hori, et al., "Present Status of 150 MeV Racetrack
Microtron", Proc. 22nd Linear Accel. Conf. in Japan,Sendai (1997) pp.16-18.
[5] T. Takayama, et a!., "Compact Synchrotron Radiation
Source 'AURORA-2' with 2.7T Normal Conducting
Bending Magnets", Proc. 1996 European Part. Accel.
Con f., Sitges, Spain (1996) pp. 709-711.
[6] H. Tsutsui, et al., "Aperture Calculation of AURORA2D Compact Electron Storage Ring with a Superconducting Wiggler", Submitted for 1997 Part. Accel.
Conf., Vancouver, Canada (1997).

AURORA-2D has already been disassembled in mid
September immediately after the completion of wiggler test.
It will reappear as AURORA-2S in early December. It is our.....1

L_ ________________llllL---------------~
Fig. 1 Plan of AURORA-2D with wiggler.

Fig. 2 Whole view of AURORA-2D with wiggler.

-535-The 11th Symposium on Accelerator Science and Technology, Harima Science Garden City, 1997

l.loni!OICOI\ItOI

Plll'ltn• 15011

llllncontrol
f'1111tlur11 15011

RING

IIEAMIOfiTOR

Fig. 3 Control system of AURORA-2D

32.5

EiJ

Fig. 5 Schematic of AURORA-2S
2

u::
0-~

c

1.5

bJJ::E"'

0.5 L_,_~...L.~.......L~~.i....L...~...L.~--<-.L~~-'-'-~....W...u
100
200
300
400
500
600
700
800
Current [A]Fig. 4-a) Dynamic excitation characteristics of 2. 7 Teslabending magnets.

1000

BOO

600

~400=~(.)

200

Time [sec]Fig. 4"b) Ramping pattern of both 2.7 T bending magnets
and 7 T wiggler.

EnergyCircumference
RF voltage
Harmonic number
RF frequency
Energy aperture
Energy loss
Synchrotron frequency
Mome.ntum compaction
Tune horizontal
verticalNatural chromaticity
horizontal
verticalNatural emittance
Energy spread
Radiation damping time
horizontal
verticallongitudinal
Bunch length
Touschek lifetime at IA
Quantum lifetime
Field strength BM
QF
QD

A2D
0.7

0.7

21.94622014191.243
5.937
24.4240.14651
0.16528
1.590
1.550

21.94622014191.243
5.502
29.0710.154930.18530
1.590
2.100

-1.4
-2.8
474.022
0.421

-2.3
-3.8
934.564
0.444

5.873
4.196
1.836
32.4035.712>1E+32
2.7

5.599
3.525
1.487
36.1649.903
7.0E+24
2.7

9.4
-8.6

-12.3

JW7T

10.9

GeV

mkVMHzMeV
keY/turnMHz

1tnm rad
MeV
msec
msec
msec

mmhourhourTesla
Tesla/mTesla/mTable 1 Parameters of AURORA-2D with and w/o wiggler-536-