The 12th Symposium on Accelerator Science and Technology, Wako, Japan 1999

Direct Beam Injection Lines to PF and AR Rings
Kuninori ENDO, Atsushi ENOMOTO, Takuya KAMITANI, Masahiro KATOH*,
Mitsuo KIKUCHI and Motohiro KIHARA
Accelerator Laboratory, * Institute of Materials Structure Science
High Energy Accelerator Research Organization
1-1 Oho, Tsukuba-shi, lbaraki-ken 305-0801 JAPANAbstract
When the KEKB experimental operation becomesroutine, it will require a frequent injection of both electron
and positron from a linac. It will interfere with the injection
to PF and AR rings taking a lot of time for converting theinjection modes at different energies. To accomplish all
injections in a short possible time, a new injection beamlines are investigated.

1 Introduction
With the onset of the KEKB routine operation frequent
electron and positron injections will be required to make up
for a short beam life time at the high luminosity run morethan -1032 s· 1cm·2• At present both AR and PF rings arefilled with electrons at 2.5 GeV and KEKB with electrons of
8 GeV and positrons of 3.5 GeV. An injector linac,
formerly built for PF ring and also served as an injector toan accumulation ring (AR) of the TRISTAN main ring(MR), has been modified greatly to inject electrons andpositrons at their full energies. As a result an electron gun,pre-buncher and buncher for 2.5 GeV to PF and AR
injections are installed at an intermediate position of thelinac. During injection to PF or AR, most of linac sectors
are suppressed of the accelerating voltage except for required
ones to attain an injection energy. The PF injection is few
times a day, about 10 min for each fill, but the AR
injection many times a day at present because of its shortbeam lifetime.
To overcome the complex and time-consuming mode
exchange, the direct beam injection lines to PF and AR areconsidered. Installing a new beam transport line parallel tolinac, the electron beam extracted at 2.5 GeV with a kicker
magnet is transported along this new line and switched to
PF or AR with a bending magnet at the beam switch yard.
The electron beam switched to PF is transported through thepresent beam lines. But to AR several dipoles andquadrupoles need to be manufactured to guide the beam tothe last curved transport section which is available bychanging the excitation parameters.

2 Extraction from Linac and Transport to Switch Yard
The pre-buncher and buncher at the sector C-8, justdownstream of quadrupole QF-C7-4 (see Fig.l), are replacedwith a kicker magnet whose excitation duration is shortenough to allow for an extraction of one beam pulse from50 Hz pulse train without effecting rest beam pulses toKEKB. At this point the beam energy should be adjusted to
2.5 GeV for every injection mode (the present value is2.85909 GeV). This energy reduction can be compensatedby the following sectors. A trigger signal to fire the kicker

magnet can be supplied by the ex1stmg timmg systemallowing the beam injection to a selected bucket of the PF
or AR ring. A diagnostic beam energy measuring device canbe provided after the kicker magnet to feedback for the beamenergy regulation. One electron bunch is extracted
horizontally and bent back to a straight beam transport line
parallel to linac. Distance of the new beam line from thelinac axis is assumed as 2.3 m for the present study. Thelinac beam level from the floor is 1.2 m. If the higher beamlevel is required to make the stay clear space under the newbeam line, the vertical beam offset is possible using thevertical bending magnets following the horizontal bending
magnets. The beam level is assumed as 1.8 m by thevertical offset of 0.6 m so as to maintain this level halfway
to the PF injection line and to the beginning of the existing
last curved section of the AR injection line.

Fig.l Section of the electron beam extraction. PB (prebuncher) and BU (buncher) are replaced with a kicker
magnet (about 2 m long). An available space is 4.2 m.

Distance(m)Fig.2 Twiss parameters of a new beam transport line alonglinac. A cell length of the regular sectton is 17.6 m (21triplets in total).

After the beam is elevated, the irregular section
containing the horizontal and vertical dipoles is connected to
the regular section through the transition section. As theregular section is very long (about 370 m), a compact
regular cell of a quadrupole triplet is considered toaccommodate one beam position monitor per cell enabling
both horizontal and vertical readings at the center of themiddle focusing quadrupole. Twiss parameters of the beamtransport line (about 500 m long) is shown in Fig.2 which
are obtained by TRANSPORT code. All magnet elements ofthis transport line is given in Table 1, where B 1 is thekicker magnet and BV 1-2 are the vertical offset magnets.

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The 12th Symposium on Accelerator Science and Technology, Wako, Japan 1999

Table 1MAGNEfPARAMEIERS OF NEW BEAM TRANSPORT
LINE AWNG LINAC. FIGURES FOLLOWING THE
ELEMENT NAME ARE THE NUMBER OF MAGNETS.
0) Horizontal offset section
Element K-value Ang (deg) Length (m) Grad IT/m) Field (T)22.971
Fl x 20.551
0.20-20.944-0.5020.20~D1-0.500
1-6.871
2.00
0.500
B26.871
2.002) Vertical offset & transition section-10.820
D1-0.260
0.20
16.19710.3880.20-19.247
2-0.4620.20
20.857
F2
0.500
0.20
-19.248
D3-0.462
0.20
15.603
F30.3740.20-20.841-0.5000.20
14.731
F40.353
0.20-9.4395-0.2260.20-0.497
1X 2-4.096
1.20
0.497
BV2x2.4.096
1.201) Reg_ular section (21 triplets)
13.971F6 x"22 0.670
0.40-14.193
D6x 43 -0.340
0.208

assuming the momentum spread of ±0.2%. The normalized
horizontal and vertical emittances are assumed as 800 and820 mm mrad, respectively. Magnet parameters of PF
injection line are given in Table 2 with the present data. The
beam switch magnet is given by the name of BSW.
·g 80,..

i60><"' 40_L-=.::=...t.:t,,oo~----::c,.!::co~---;!;;,oo;---------;,•oo:,;--~;;;;;,••;'--"-~.oo~'------;;7oo -6·- ·------~----- --. -·-· --------·-------+4-----------.
Distance (m)2.5 o~v new beam line

PF lnjecllon line

Fig.5 Twiss parameters to the PF ring from the beginning of
the C-sector through the new beam line.

3 PF Beam Injection LineAt the beam switch yard the first dipole magnet
following the last quadrupole triplet of the linac beam line
serves as a beam switching element. It is operated as abipolar mode and the beam is dumped when it is not excitedor in the case of power supply faults. If it is excited ineither polarities, the beam is deflected to the PF or AR
injection line. Fig.3 gives the location of the beam switchmagnet.
Bipolar beam switch magnet

New AR lnjet:tlon linee.

g·il'

J~

2~~_,_..._....L......__.__,

200_ __,_J_.__,___, ...... _l. ~ ...... ~--'-----~--'-300

400

Distance (m)Fig.6 Beam size from the beginning of the C-sector to the PF
ring through the new beam line. The effect of themomentum compaction is not considered.
Table 2MAGNET PARAMETERS OF PF INJECTION LINE.
First section
lement K-value Angle Lenfith Gradient Field Present(deg) (m(T) (T/m or T)(TimJ-7.7 l
ADl-0.186
0.20
AFl
0.271
0.20
11.306
Al-0.281
0.30-7.817
2.865
Bl
0.291
0.30
8.084
-5.347B2-0.056
0.30-1.551
6.155
0.088
0.30
2.447
3.030
Cl-5.212
C2-0.188
0.30-5.596
0.130
3.612
3.218
C3- 0.30
sw
5.000 2.00
0.364
BH1x2
7.506 1.05
1.040 1.040
BH2x2
1.039 1.040- 7.501 1.05
26 Second section
1-0.174-4.827-2.4490.30
7.493
D20.2700.30
2.604-8.340
D30.300
0.30-7.260
D40.262
0.30
7.279
6.153
1-0.303
0.30-8.423-8.432
2
0.212
0.30
5.903
5.087
1-0.303
0.30-8.423-8.432
Fl
0.270
0.30
7.493
7.896
F2-0.313
0.30-8.712-8.879
0.269
10.30
7.480
7.514
2-0.275
0.30-7.655-7.517
0.352
0.30
9.785
9.605
3
4-0.200
0.30-5.565- -5.152-0.860 -1.037
1- -6.211 1.05
BV2
6.211 1.05
0.860 1.037
BH3 x26.002 0.84
1.040 1.040
BSPl-0.679 -0.679- -7.000 1.50
BSP2-5.000 1.00-0.728 -0.728

2)Present PF llljecllon line

Fig.3 Location of the beam switch magnet at the switch yard.
To the PF injection line, the beam passes over theKEKB injection lines with the vertical separation of 0.6 m.
The PF ring beam level is higher than the linac axis by 3.5m and the beam is vertically translated along the slope asshown in Fig.4. The 1.8 m beam level, therefore, will bemaintained to the first vertical bending magnet (BVl).

Jl7o1.,. Pfrlng·hVertical plane-=6: ...j£ PF "&;in..

------r·::c.

Fig.4 FP injection line. BVl is the location of the firstvertical bending magnet. Difference of beam level
between linac and PF ring is 3.5 m.

4 AR Beam Injection Line

Twiss parameters and beam sizes from the beginning of
the C-sector to the PF injection septum through the newbeam line is shown in Fig.5 and Fig.6, respectively.
As the effect of the momentum dispersion is notconsidered, 11x(l¥JI p 0 ) and 7Jy(flp/ p 0 ) must be !d:led tothe beam size in Fig.6. The maximum 11x is about 3.8 m,
so the maximum half beam size increases to -9 mm

As shown in Fig.3, the beam is guided by the alternate
excitation of the beam switch magnet. As the present
injection line is common to the KEKB electron transportline except for the last curved section, this switch magnet
has to be followed by a new 2.5 GeV AR beam line whichis connected to the existing last curved section at 1.8 m
beam level. Twiss parameters and beam sizes are given inFig.? and Fig.8, respectively, from the beginning of the C--469-The 12th Symposium on Accelerator Science and Technology, Wako, Japan 1999

sector to the end of the AR injection line. Also in Fig.8,TJx(Ap/ p 0 ) and TJy(llpl p 0 ) are not considered.

all quadrupoles. Ten cases were treated for different random
numbers.
'r-c--~~--.------.--~~~···,·-r-----r------;~·~··-~~~~-.-----,-~--§ " 1---'.I'M---i----+---- +--..;;.v· rr+---iL"""<f>o"'w]
i;i ..

Distance(m)2.5 GeV new beam line

Fig.8 Beam sizes of the AR injection line from the beginningof the C-sector of linac.

Distance (m)Fig. 7 Twiss parameters of the AR injection line from thebeginnmg of the C-sector of lmac.
The AR injection line is divided into 3 sections (Fig.9),
curved section-1, straight section and curved section-2. As
the curved section-2 (last curved section) is independent of
the KEKB injection lines, it is used by adjusting theexcitation parameters so as to connect twiss parameters at
both ends as given in Table 3, where the first twoquadrupoles (QADI and QAFl) and the beam switch dipole(BSW) are same as in Table 2.
The straight section has enough length (about 100 m) toaccommodate several regular cells. Although it is possible
to use quadrupole triplets, a small number of FODO cells is
adopted allowing larger betatron function.
Table 3MAGNET PARAME1ERS OF AR INJECTION LINE.
0) Curved section-1
Element K-value Ang (deg) Length (m) Grad (T/m) Field (T)ADl-0.186
0.20-7.761
AFI
0.271
0.20
11.306
D2-0.346-8.2550.35
F20.400
0.35
9.524
D3-0.470-11.202
0.35
XFl
0.130
0.50
2.169
XD2-0.332
0.50-5.543
XF20.234
0.50
3.895
XD3-0.256
0.50-4.267
XF30.320
0.50
5.338
XD4-0.279
0.50-4.652
XF40.232
0.50
3.871
XD5-0.198
0.50-3.295
XF50.1330.35
3.173
sw-5.832
2.00-0.424BA x 5-5.832
2.00-0.424
2) Straight section
XD6-0.272
0.50-4.545
XF60.443
0.50
7.380
XD7-0.377
0.50-6.282
FAI
0.274
0.50
4.562
DAI-0.125
0.50-2.076
WFx40.0970.50
1.615
WDx3 -0.109-1.813
0.50,) Curved section-2
RD1x2 -0.128
0.36-2.955
RF20.2560.36
5.926
RF30.173
0.364.004
RD4 x2 -0.219
0.36-5.077
RF50.227
0.36-5.259
RF6-0.310
0.36-7.172
FOl X 3 0.309
0.36
7.166
DOl x 2 -0.285
0.36-6.600
D02 X 2 -0.296
0.36-6.864
F020.288
0.36
6.681
F03
0.354
0.36
8.208003-0.3180.36-7.372
HRI x 45.384
1.000.783
BVRU x 2-4.779
1. 00-0.695
BYRD x 24.779
1.00
0.695
BHR2x 14
6.429
1.00
0.936
BHR3
7.558
1.00
1.100
BR2E
4.368
1.200.530
BRIE
2.406
1.20
0.292

5 Effects of Random Alignment and Excitation Errors
To estimate the orbit deformation due to the quadrupole
misalignment and excitation error, random error are given toFig.9 Layout of the AR and KEKB injection tunnel.

5.1 Quadrupole Misalignment
It is assumed that every quadrupole has alignment error
in all directions between -0.3 - 0.3 mm. The rms orbit
distortions are given in Fig.lO for the PF injection line andFig.ll for the AR injection line. Large misalignment
effects are expected from these figures.

Distance (m)Fig.l 0 Orbit distortion due to the random quadrupole
misalignment for the PF injection line including
new linac beam transport lme.

815

§

:§
§

w

"'

i ' r· .... cc'··''J\ ~"Yo:/~".,' ..
Distance (m)Fig.llOrbit distortion due to the random quadrupole
misalignment for the AR injection line including newlinac beam transport line.

5.2 Quadrupole Gradient Error
Under an assumption that every quadrupole has a random
gradient error between -0.01-0.01 Tim (percent error depends
on the excitation level), effects on the betatron anddispersion functions are examined. According to thecomputer simulations, effects of the random gradient errors
are very small for above error range.

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