Alignment of injector linac
KEKB Accelerator Review
24 February, 2015
Toshi Higo (Injector linac group)Contents
1.
2.
3.
4.
5.

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Initial alignment along laser line
Hard ware alignment on each girder.
Floor movement
Near future development
Conclusion

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2J-ARC

Linac layout and alignment requirement
120mB
ACRings
12500m345

σ < 0.1 mm: βγε 20 mm·mrad is almost
satisfied.
σ > 0.1 mm: emittance preservation isrequired by some methods.

Requirement
Local σ < 0.1mm
Global σ < 0.3mm
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4Reflectors forlaser tracker use

Reference pointof girder

Hard wareMechanicalreference 321Laser PD

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Girder

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1. Girder set to laserreference by PD
2. Support set w.r.t. mecha.
reference
3. Hard ware aligned withmecha. reference
4. Hard ware alignment
checked by tracker
4Hard wares around standard 9.6m girder
Acc Structure

4-segmented silicon
PD (dia.=10mm)
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Standard unit
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Arm from PDto reflector
5Major steps since last review
1. Established 500m laser straight reference line over C—5
2. Established reference points for DR
3. Installed target/FC followed by LAS with Solenoid and largeaperture Q magnets
4. First girder alignment done in 3—5 sectors by laser PD
5. Hard ware alignment on each girder done with laser tracker
6. Done alignment on old Q magnets with laser tracker
7. Done stiffening of girders, especially positron line
8. Completed initial alignment of 3—5 sector with laser PD
9. Further evaluated floor movement
10. Installation of heavy radiation shield on positron
generation system underway
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Stiffening of 9m-girder
Soft: metal plate spring
Stiff: slide roller withbolt fixing
Eigen mode frequency
Several  more than 10 Hz

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End hor. slider

Center pivot

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Positron generation and acceleration
FCNew aluminum
girders

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Solenoid

Road cell with ball
 Jack bolt
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1. Initial girder alignment

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Straight laser reference line
• 500m laser line was stabilized by feed back.
• We can routinely measure C-5 sector by laser PDsystem• Some developments may still be needed– Easy sensitivity calibration and absolute zero position– Cares against radiation damage• However, at a moment– Because the system is most practical, we utilize it for
initial alignment– Automatic in/out devices were developed to monitor
floor motion continuously
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500m straight reference line by laser

Gaussian beam
Tilt feedback

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PD sensitivity
Fitted with Rayleighfunction along 500m linac
was used in the presentanalysis
Recent estimation frommechanical girder
movement in 3—5 sectorSensitivity varies by afactor 2 , but the center
identified as zero output
voltage should be OK
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Finished initial alignment of girders
1. Girders in sectors 3—5 were quickly aligned
in 2011 after the earthquake.
2. Positron generation area was installed by thesummer 2014.
3. Until late July 2014, C—5 sectors werealigned with leaving V-shape residual.
4. In late Jan. 2015, all in the 3—5 sectors werealigned straight, except for the C-band unit
at 44.
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3—5 alignment in Summer 2014C12345C-2 sectors were aligned bylaser PD, but 3-5 sectors werekept with preliminary alignment
correction since earthquake.

After alignment in summer 2014.
Big spike-like misaligned points
are those to be corrected
between standard girders.
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Present 500m alignment over C-5
after completion of initial alignment in late Jan. 20142015/2/24

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Summary of girder alignment• Girder alignment can be done with the present
laser PD system probably within 0.2mm in sigma.
• Residual misalignment of the first initialalignment was 0.3mm in sigma, mainly comesfrom those aligned earlier but moved later in ayear scale.
• Floor moves in a big scale, especially atexpansion joint, so that the swift measurement
is needed, or the movement should be taken
into account.
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2. Hard warealignment on girder

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Hard ware alignment on each girder• Accelerator structures in units at sectors 3-4-5
were corrected during summer shutdown in
2014, followed by those in sectors A-B-C-1.
• Reflector base was put on the top of old Q
magnets. Their alignment was measured andmostly corrected.
• New Q magnets with big bore were set w.r.t.
the mechanical reference on girder.
Confirmation is yet to be done.
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Reflector setting for hard ware positioning

Mounted oncoupler OD

Reflectors for
old Q-magnet

Arm from PD
to reflector
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ACC str. In unit 34 Horizontal
ACC Structure
Before adjust

WE

After adjust

10m size
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ACC str. In unit 34 Vertical
ACC Structure
Mecha. reference
After adjust

UPDN

Before adjust

10m size
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Hard ware alignment on a girders in
Horizontal sector 3—5
VerticalHorizontal
σ=34µm2015/2/24

Vertical
σ=47µm

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Alignment error estimation
w.r.t. reference straight line

1. Laser straightness
Pointing stability being fedback  σ~0.05mm
2. Girder alignment error
Setting errors  σ~0.3mm
PD sensor setting error on holder  σ~0.015mm
Radiation damage of PD sensors  ?
3. PD center to girder for setting laser tracker reference
Arm setting error  σv~0.05mm
4. Girder reference to hard ware setting
Tracker confirmation of reference position  0.05mm/5m

5. All the above in random manner~0.3mm which will be improved by morealignment times to probably 0.2mm level, unless
any systematic error is left
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3. Floor movement

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Floor moves significantly• It has been long pointed out.
• Laser PD monitor over half a year showed– Significant movement being localized atjunction– Mostly vertical (upward from summer towinter) by a few to several mm.

• Following pages show the movements.
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Variation in half a year
from July to January

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Floor horizontal movement

in half a year from summer to winterC3

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Floor vertical movement

in half a year from summer to winterC3

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48

28

Long-term floor movement near junction

Upward drift at junction~0.3mm/monthNot evident but~0.05mm/month
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Junction and after-pouring concrete

Expansion joint between
two solid plates
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15cm step not well
stick on the base plate

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Tunnel basic structure
Klystrongallery

Solid base

15cm-highafter pouringconcrete

Concrete shield
40-50mdeep piles

TunnelBase structure

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PD for continuous measurement
PD_28_REFUA
PD_28_G6DA

Located at
28 Expansion joint
Nov. 2014

Automatic
IN/OUT
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Daily motion between junction

Little hor.
correlation

Upstream
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Downstream from junction

Downstream

Downstream

Upstream from junction

Well correlated
in vertical plane

Upstream
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Ver. daily
Oscillation~ 0.1mm/day
Some correlatedmotion
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Longer-term motion
Horizontal

Horizontal

Vertical
40 days
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Exists some drift
0.1~0.15mm/mo
0.1mm/1000hr/250m
A~10-5µm2/s/m
in ATL law

Vertical
15 days
KEK Review HigoMay not be only
diffusive
Should see how it
varies in a year range
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Estimation of floor movement
some typical observed values
Unit mmHorizontal

VerticalDaily

0.10.1

Week0.10.1

Half a year0.52Speed

0.01mm/hour

0.01mm/hour

We should study/develop the linac systemwith these values in mind.
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Trial to understand the expansion joint
Junction
EastwallDown
NotrthBeamWestwall

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Junction relative movement at 28
19 Sep. 2014 – 31 Jan. 2015

↑ Up, East, North(beam line)

Up

0.4

North(beam)
East

0.3
0.2
0.1
0.0-0.1

Water flood due
to typhoon-0.214 Sep.
↓ Down, West, South

Linac stop
Air cond. restart
23 Nov.

1 Feb.

Found daily movement, month-long drift, climate effect, etc.
These are related to those observed in laser PD long-term result.
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4. Near futuredevelopments

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We should study and develop curesagainst floor movement• Near future for Phase-I– Make quantitative analysis at more places and morein systematic manner– Try to monitor movement with beam
– May study other monitor methods, such as HLS• Development for phase-II and -III
– Beam steering by targeting golden orbit– Movers, at least locally– Sophisticated compensation such as offset injection
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Possible time frame in mind
2015201620172018
1 2 3 4 5 6 7 8 9 # # # 1 2 3 4 5 6 7 8 9 # # # 1 2 3 4 5 6 7 8 9 # # # 1 2 3 4 5 6 7 8 9 # # #MR
DR
Linac Alignment

Phase-I 1nC

Phase-II 2nC
DR comissioning*****5nC

RF Gun for electron
More positron beam
Low emittance beam study
Study for lower emittance and higher charge
Initial alignment
Toward full beamContinuous measurement
PD fabrication
More measurement points
Strategy discussion
Design monitor and mover
A few test system fab.
Install
Test feedback
Hard ware preparaiton
InstallActual usage
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Concluding remarks on alignment
1. Girder stiffening done.
2. Most of the hard wares set in the beam line, except for pulse-Q.
3. Initial girder alignment done with the residual ~0.3mm in sigma
over 500m line.
4. Hard wares alignment on each girder improved to be 0.05mm insigma.
5. Local smoothness will be improved by laser tracker.
6. Floor moves a few mm in half a year, mostly at expansion joint,
while the daily motion ~0.1mm.
7. Floor movements should be evaluated at more points and withbeam study to develop a practical cure method.

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