Alignment and support(Injector linac)
5 March 2013
KEKB Injector group
T. HigoContents• Requirements• Alignment status– Laser PD (photo detector) for long-distance– Laser tracker for local but also for long distance– Cross checking two methods– Alignment tool over a long period• Perspective and conclusion

T. HigoKEKB Review 5 March 20132

Requirement on alignment• KEKB– 0.1mm but not kept established to date
– Actually big misaligments were observed such as• A few mrad kink along linac• Misaligned Q’s, ACC’s and girder of mm order• SuperKEKB– It depends on sz, fRF, correction, etc.
– Requirement• Global (long-distance) s=0.3mm(rms)• Over a sector s=0.1mm(rms) / 100m length

T. HigoKEKB Review 5 March 20133

H. Sugimoto, 2 Nov. 2012

Sector Cto5: -10 deg rf phase
R56 =-0.20

Emittance & Misalignment (Typical example)
100 samples

Presentation
by M. SatohQualitatively consistent with a famous formula derived by A.W. Chao.
T. HigoKEKB Review 5 March 20134

Strategy to meet this requirement• Long-distance alignment– Use laser straight line to align accelerator girders• Local alignment– Precisely set hard wares mechanically on the girder– Laser tracker to check hard ware alignment w.r.t.
girder reference– Improve smooth local alignment with laser tracker• Refinement– In addition to the above tools– Beam information is used
T. HigoKEKB Review 5 March 20135

Shifting from recovery phase to SuperKEKB• Recovery reported in the last year review (2012)– Girder rigidity increased– Started beam acceleration for Photon Factory• Now toward better alignment (2013-2014)– Recover the upstream part of the linac– Re-establish the alignment method basically the samefor KEKB

• Established alignment technique (2014)– Confirmation through beam study– As a tool useable for a long period of years• Further development? (2015 -- )– Intermittent alignment will be done
– Develop as needed
T. HigoKEKB Review 5 March 2013

6Girder alignment and hard wares on the girder
Reflectors forlaser tracker

2Hard ware
Reference point ofgirder for tracker

Mechanicalreference
Accelerator
Girder1Laser PD
T. HigoKEKB Review 5 March 2013

1. Girder alignment withlaser PD
2. Hard ware alignedw.r.t. girder reference
3. Checked by tracker
7

Development in practice
1. Re-establish laser PD system in a long distance
2. Based on this, proceed initial alignment of girders
3. Hard wares are set on each girder mechanically andchecked by laser tracer
4. Cross check between laser PD and laser tracker fora long-distance measurement
5. Beam introduction (2013)
6. Explore the better method for long-term usage
7. Reduce local misalignment by laser tracker
8. More beam transmission (2014-2015)
9. Further introduce beam-based techniques
10. Reaching to goal (2015--)
T. HigoKEKB Review 5 March 2013

8Linac layout and alignment philosophy

120mJ-ARC

BCARings
12345500m

1. Establish method at AB sector
2. Establish full length C-5 500m line

T. HigoKEKB Review 5 March 20139Philosophy: Accelerator structure girder as
an alignment unit
AB Line136m

Sector C
82m

500m C-5 Line

Basic unit, girder 9600mm

Laser
PD
T. HigoPDKEKB Review 5 March 201310

Hard wares around beam lineand alignment reference line
4-segmented sillicon
PD (dia.=10mm)

Acc StructurePDPD

T. Higo基本ユニット
KEKB Review 5 March 201311

Alignment method on the girder
Laser tracker mountACC Structure

Reference bar
Reference planeSub-support

Adjustment screw
Girder
Girder table

Laser tracker reference
precision-aligned to thelaser PD line

Two basic alignment tools in hand

1. Laser PD system forstraight reference line

T. Higo2. Leica AT401
Laser tracker for general use+ alignment on unit girder

KEKB Review 5 March 201313

Establishment of laser PD method• Technology developed for KEKB
– Not used routinely  Re-established and improved• Round and narrow laser beam
– Newly developed laser optics in collaboration with AIST
(Advanced Industrial Science and Technology)• Refurbishing PD– Select the PD’s used for KEKB without gain deterioration• Minimize mounting error• Replacement of cable with flat cable– Estimate the accuracy +-0.3mm in mind

• Now initial alignment was started with laser PD– AB sector 120m  Alignment done once
– C5 sector 500m  Laser profile proven

T. HigoKEKB Review 5 March 201314

Laser system
He Ne laser (for C5) 9mW
Picomotor (NewPort):
Dynamic range = 13mmResolution
1.8 nrad / H step (30 nm)
0.7 nrad / V step (30 nm)

Δ=±0.5mm

Beam expander
YX

Gaussian beam less than
40mm size was transmitted
through 500m line.
Pointing stability
established by feedback bymonitoring at the end.

T. Suwada, 6 Nov. 2012

Passage of He-Ne Laser over 500m
40mm by eye at theinjection point

40mm by eye at the500m-long linac end

Laser system

Vacuum laser pipe

Spot sizeon 1 March 2013
Round beam with
4sx〜21mm4sy〜18mm
Small enough for 10mm PD sensor.

T. HigoKEKB Review 5 March 201316

Laser pointing stability
C-5 line (500m) with FB control

s=40μm,+-0.1mm(max)Measurement: 100 samples in 3sec.

The system <0.1mm was proven with feedback on laser pointing.
T. HigoKEKB Review 5 March 201317

Initial alignment of girders in progressusing laser PD• Laser beam set with feedback.
• PD sensitivity measured as needed• Adjust girders to zero PD output• Each girder is assumed to be aligned
within +-0.3mm– This error estimated from the gain balance offour sensors.

T. HigoKEKB Review 5 March 201318

Long-distance alignment measurement
by successive laser tracker measurements
One of the way to cross check

N-1N

N+1

Reflectors at girder

Laser tracker

Laser PD line
Reflectors on wall
T. HigoKEKB Review 5 March 201319

Comparison in long-distance alignment
Unit girder vertical position along AB sector
Meas. By laser tracker-X- Reading by Laser PD system

mm
1.2
1.0
0.8
0.6

0.4
0.2

Most of the bad PD data are omitted.

0.0

0m

100m

Downstream ------------------------------- Upstream
T. HigoKEKB Review 5 March 201320

VerticalLaser tracker nominal points

T. HigoKEKB Review 5 March 201321

Horizontal
Laser tracker nominal data points

T. HigoKEKB Review 5 March 201322

Cross checking in a long-distance• Alignment with laser PD along 120m line done.
• Cross checking is on-going– Between 1. Laser PD & 2. Successive laser tracker– These agree within as large as 1mm.

• The origin of this large error is under study.
• The same studies are underway in– C-2 (250m), C-5 (500m), and AB (120m) again• Our target of this cross checking– being consistent within 0.3mm rms

T. HigoKEKB Review 5 March 2013

23

Thinking from laser tracker precision spec.
Leica AT401 precision spec
Measurement in 10m scale: σ～4μr
Local alignment between two adjacent girders
Relative precision
Precision of components ～ 80μm

Successive 500m alignment use
L＝unit length～10m, C5 sector 8×6＝48 units
Error propagation over 500m in random walk√48 × σ × L ～ 7×4μr×10m → 280μm

Seems feasible for long scale but needs to bepractically confirmed by comparing to the laser PD.
T. HigoKEKB Review 5 March 201324

Hard ware alignment on girder
Short-distance local alignment• Mechanical setting of beam-line
components• Support frame is pressed to mechanicalreference on the girder– Structure support geometry error +-0.05mm• Then hard wares are supposed to sitaligned within 0.1mm

T. HigoKEKB Review 5 March 201325

Present situation on short-distance (local) alignment
Hard ware alignment on a 10m girder
B2-H

0.266

0.228

B2-V

0.136

B4-H

B4-V

Reference bars (blue) are set typically within 0.1mm.
Ver < 0.2mm
Hor. up to 0.5mm slope

Systematic error may exists in H by 0.5mm, whileV stays 0.2mm from reference bar.
T. HigoK. Kakihara, 22 Nov. 2012

KEKB Review 5 March 201326

Hard ware alignment on girder• The end two points are referred for alignment of hardwares on the girder.
• Reference plane (V) and reference bar (H) are defined
w.r.t. these reference points, established by laser
tracker.
• Hard ware supports are mechanically pushed along
these references• Hard wares are supposed to be within 0.1mm.
• Confirmation of this method by laser tracker isunderway. Error amounts to 0.5mm!
• Need to identify the error source and improvedown to 0.1mm max.
T. HigoKEKB Review 5 March 201327

CMM evaluation of ACC structure support
Errors seem within tolerance of +0.05mm.
(This result is under re-evaluation.)
H misalignment of 0.5mm can not
be explained.

Due to earthquake?
To be studied.

T. HigoK. Kakihara, 17 Jan. 2013

KEKB Review 5 March 201328

Long-distance alignment tool for long-term• Present laser PD system– Present method should be good for initial alignment– But not assured for long-term usage under beam radiation– Beam radiation is suspected to be the most probable reason• Apply other methods?
– Fresnel (Study suspended)• Need to smooth all the laser PD ducts to confirm 500m Fresnelsystem.

– Wire and HLS (not proceeded)• need someone to establish– DESY small ball (just thinking)– Need additional manpower to introduce any one•  should be suspended unless critical.

• Improve PD system– Practically feasible and we focus to this now
T. HigoKEKB Review 5 March 201329

PD gain reduction
After operation for KEKB in severalyears, 30% of PD’s suffer from gainreduction.

The origin is not yet identified, but wesuspect the beam radiation as one of
the relevant reasons. We hope thelow emittance will help reduce beamloss.
We need to evaluate PD radiation
resistivity, improve PD and/or reducebeam loss affect on PD’s.
30%
5V

T. Suwada, 17 Jan. 2013

Evaluation and developments on PD• PD material– Radiation-resistive PD?

• Evaluation of deterioration– Test at B8 end under consideration• Improvement– Set PD’s aside during heavy beam operation
possible– Introduce radiation resistive PD  will study– Radiation shield from beam loss  impractical– If abandon PD  laser tracker or beam
T. HigoKEKB Review 5 March 201331

PD sensor re-aligned in the holder
Alignment of PD
sensor in a holder.
Adjustment done.
Then
sx=10mm
sy=14mm

Misalignment of PD sensor in the holder is small enough.
Other error sources are to be fully studied.
T. HigoKEKB Review 5 March 201332

Other possible way in hand
Rely on laser tracker• From labor for 500m measurement point of view
• Laser PD with removing and restoring PD’s
– Each sector ends
• 12 pts for 6 sectors / 2 person X day  during long-term maintenance– Each girder ends
• Remove/restore 96 points for 48 units  17 person X day  impractical• Laser tracker with successive unit-wise measurement– 1 unit / 2 person X hour
– 6 sectors  once a year
• 48 successive measurements  2 person X 6days– A sector of interest = 8 units as needed  during long-term maintenance• 8 successive measurements  2 person X 1day

T. HigoKEKB Review 5 March 201333

Perspective• Cross check long straight-line alignment ofgirders by two methods, laser PD and laser
tracker.
• Establish the long-term usage of one of theabove systems.
• Local alignment of hard wares on the girder will
be reduced from 1mm order to 0.1mm.

• Beam-based alignment information is to be
added into the present alignment process.
T. HigoKEKB Review 5 March 201334

Time frame in summary• 2013 start beam transmission– Initial alignment based on laser PD– Compare and confirm the long-distance alignment• 2014 acquire beam information– Imprement beam-based information• 2015 supply to rings– Improve with more beam and better beam

• 2016 toward ultimate goal
– Introduce other alignment method if required
T. HigoKEKB Review 5 March 201335

Conclusion• We are proceeding initial alignment of girders
using laser PD system.

• The long-distance alignment method should beconfirmed targeting an error of 0.3mm.
• Hard wares on the girder should mechanicallybe aligned within 0.1mm.
• Long-term usage of the long-distance alignment
tool should be established.
T. HigoKEKB Review 5 March 201336