International Workshops on Accelerator Alignment (IWAA) 2012, Sep. 13

Straightness evaluation for the 206-m-long part of the KEK electron/positron linac

using inclinometersg

Tatsuya Kume1, Eiki Okuyama2, Masanori Satoh1, Tsuyoshi Suwada1

and Kazuro Furukawa1

1: High Energy Accelerator Research Organization (KEK),Oho 1-1 Tsukuba Ibaraki Japan 305-0801Oho 1-1, Tsukuba, Ibaraki, Japan 305-0801,

2: Faculty of Engineering and Resource Science, Akita University,1-1 Tegata gakuen-machi, Akita, 010-8502.

TargetEvaluate aligning straightness of linear particle accelerators (Linacs) for distance of several 100 m with accuracy of better than 1 mm

1 Introduction

Contents1. Introduction

•Straightness evaluation using an inclinometer

2. Demonstration• 71-m-long (single accelerator sector) straightness evaluation with a

straight barstraight bar• 206-m-long (multi accelerator sectors) straightness evaluation with a

straight bar and offset bars

3. Conclusion

Straightness evaluation using an inclinometerNot affected by transferring locus (= error in the scanning straightness)Not affected by transferring locus ( error in the scanning straightness)

⇒ Advantageous for long distance evaluation

Straightness:

1

1

n

xshxf

h1:Arbitrary straightness of th t t i t

1

1i

in xshxf

the start point,si: Sampling interval, (si=s)(xi): Measured tangential

angle,g ,n: Number of measurements

Error propagated to the straightness:

s: Error in the sampling interval: si,

sxn

ii

n

iisf

1

22

1

22

s p g i,: Error in the measured tangential angle,l: Measurement distance, (l=s×n)

ls (In case (xi)≒0⇒quasi-straight object)

Application to the KEK e-/e+ Linac Aligning straightness to be evaluated

Straight bar⇒Ensures continuity of⇒Ensures continuity of

aligning straightnessContact foot⇒Reduces affect of plate

shape and roughness

•Spatial low pass filterSpatial low pass filter•Reduce affects of positioning error in evaluation

Gravity referenced precise electric inclinometer (Talyvel 4)inclinometer (Talyvel 4)

Angle detector Controller

【 Acknowledgement 】•Range: ±3 mrad (±600 sec ),•Resolution: 0.5 rad (0.1 sec ),•Accuracy: 0.2 sec±3%-definition

【 Acknowledgement 】Authors thank Yukinori Kobayashi and

members of the Accelerator Division 7in Accelerator Laboratory in KEK andM hi K t h f I tit t f M l lMasahiro Katoh of Institute of MolecularScience for providing us Talyvel 4.

Straightness evaluation for the KEK e-/e+ Linacusing an inclinometer and a straight barusing an inclinometer and a straight bar

Inclinometer (Angle detector)

Cross-section of the straight bar

Straight bar

Straight bar made of 3-mm-tick Al t l i (1990 2306 lrectangular pipe (1990~2306-mm-long,

50-mm-wide, and 25-mm-high)Foot made of 2-mm-tick glass plate

(=optical parallel- = 633 nm) ( opt ca pa a e 633 )with area of 50×50 mm

Reversal measurementEliminate offset of the angle measurement system

Off t f th t d b

Eliminate offset of the angle measurement system (= Inclinometer + Straight bar + Pair of contact feet)

Offset of the system:o caused byOffset of the inclinometer,Shape error of the bar(i l di th h i ht diff b t th

mBefore

Straight barInclinometer

(including the height difference between the pair of the contact feet),Deformation of the bar

o

can be eliminated by

r

After

Contact foot

2nmr

:Angle to be measured

n

o r, :Angle to be measured,o :Offset of the system,m=r+0 :Measurement before reverse,n =-r+0 :Measurement after reverse

r

Effect of the reversal measurementsThe offset angles:0

is comparable to th l l

1

2

]

the slope angles: r .

-1

0

vera

ge [

mra

d

Slope

Offsets must be eliminated-3

-2

0 10 20 30 40 50 60 70

Av

P iti [ ]

Offset

Standard deviations of the slope angles

are smaller than those of the

Position [m]

20

are smaller than those of the offset angles

10

15

quen

cy

Slope Offset

Fluctuations of the offset angles (⇒drift)

are also reduced0

5

Fre

are also reduced.00 5 10 15 20 25 30 35 40 45 50

Standard deviation [rad]

Evaluation results for the 71 m long part of the sector C

1

10

the 71-m-long part of the sector C49 m-max 26 m-avg

1

0

htne

ss [m

m]

5

10

quen

cy

-2

-1

Stra

igh

Inclinometer

Telescope

Laser0

0 5 10 15 20 25 30 35 40 45 50

Freq

1 mm

-30 10 20 30 40 50 60 70

Position [m]

0 5 10 15 20 25 30 35 40 45 50

Standard deviation [m]Distance: 71 m

Histogram of the standard [ ]

Comparison between the other methods,“Laser” stands for the results by our laser alignment system

gdeviations for each position

•Agreed with the two results within sub-mm.•Straightness can be evaluated with standard deviations of 26 m-avg, and 49 m-max.and 49 m max.

*The earth curvature was compensated considering the earth as a sphere with a radius of 6371 km for the result by the inclinometer.

Error estimation1,000

• 0.6 mm-2 for 500 m ⇒Can be adopted for evaluating the KEK linac

300 m20

100raig

htne

ss [m

] 300 m

10

15

Freq

uenc

y 9.2 rad-avg

Erro

r in

the s

tr

0

5

0 5 10 15 20 25 30 35 40 45 50

F

101 10 100 1,000

Measurement distance l [m]500 m

Error propagated to the straightness

Standard deviation [rad]

Histogram of the standard deviations for the derived slope angles

Error propagated to the straightness:

lsf

Error propagated to the straightness -experimental and estimated value.

•The experimental value agrees well

l: Measurement distance,s: Sampling interval ⇒ 1.9 m-avg,

: Error in the obtained angle

f p gwith the estimated one.

: Error in the obtained angle⇒ 9.2 rad-avg The estimated value is reliable.

Offset bars for avoiding obstacles on the imeasuring pass

Evaluation distance is limited by obstacles on ted by obstac es o

the measuring path

A pair of offset bars shifts the measuring path and

avoid obstacles

Shape errors, deformations, and slope angles of theand slope angles of the offset bars will affect the measurements

Reversal measurementconsidering slope angles of the offset bars

Offset of the system caused byOffsets of the inclinometers

considering slope angles of the offset barsBefore Straight bar

Offsets of the inclinometers,Shape errors of the bars,Deformations and slopes of the bars

Offset bar

Inclinometer

mb

mc

can be eliminated by

Offset barma

rd d can be eliminated by

ncmcr 2

sd d

After s

d nbnamamb

2

na

nc

t: Slope angle (angle to be measured),ma, mb, mc: Measurements before reverse,na, nb, nc: Measurement after reverse,d: Length of the offset bars

nanb

r d: Length of the offset bars,s: Length of the straight bar

Straightness evaluation for the KEK e-/e+ Linacusing a pair of offset bars

Inclinometers(Angle detectors)

Inclinometer(Angle detectors)

(Angle detectors)Straight

bar

400

1.8 m-avg

400 mm

Straight barOffset bar

Offset bar

Deviation of the derived slope angleand Error estimation

• 0.9 mm-2 for 500 m ⇒Can be adopted for evaluating the KEK linac

1,000

m] Error propagated to the straightness: 450 m

100

stra

ight

ness

[m

p p g g

l: Measurement distance

lsf

450 m

Erro

r in

the

sl: Measurement distance,s: Sampling interval ⇒ 1.8 m-avg,: Error in the obtained angle⇒ 15 rad for single measurement point

101 10 100 1,000

Measurement distance l [m]

g p

500 m

Error propagated to the straightness -estimated value.

Straightness evaluation for the 206-m-long part of the KEK e-/e+ linac

15

of the KEK e /e linac●:Inclinometer*-Mar. 26-28, 2012.▲:Telescope Apr 18 19 2011

10

mm

]

Distance: 206 m

▲:Telescope-Apr.18,19, 2011.◆ :Laser alignment system-Aug. 9,11, 2011.

0

5

shap

e [m Distance: 206 m

5 mm

-5-20 0 20 40 60 80 100 120 140 160 180 200 220

position [m]-from 33U(3-3-0)

•Similar trend.•Partly agreed within sub-mm range.

Fairly reliable with each other

*The earth curvature was compensated considering the earth as a sphere with a radius of 6371 km.

Conclusion1. Reversal measurement is effective for eliminating offset and reducing drift

of the angle measurement system.g y

2. Obstacles on the measuring path can be avoided by pair of offset bars. Itcan extend evaluation distance of the systemcan extend evaluation distance of the system.

3. By considering slope angles of the offset bars, affects of the shape errors,deformations and slopes of the offset bars can be eliminateddeformations, and slopes of the offset bars can be eliminated.

4. 206-m-long straightness evaluation of the KEK e-/e+ Linac wasd t t d ith t d d d i ti f 15 d f th d i d ldemonstrated with standard deviation of 15 rad for the derived slopeangles.

5. It is applicable for evaluating the whole 500-m-long KEK e-/e+ Linac with2 of better than 1 mm.

IssuesIssues

1. Demonstrate longer (500 m or longer) straightness measurement

2 Estimate/evaluate the system’s performance precisely for longer2. Estimate/evaluate the system s performance precisely for longermeasurement distance.

3 Consider/realize horizontal straightness evaluation method3. Consider/realize horizontal straightness evaluation method(Straightness in the horizontal plane)

Straightness measurement using inclinometers adopted for the KEK e-/e+ linacadopted for the KEK e-/e+ linac

69-m-long part of the Sector B, (Aug. 25-28, 2009)

71-m-long part of the Sector C (Mar 29-31 2010)71-m-long part of the Sector C, (Mar. 29-31, 2010)

206-m-long part for the longer straight section (Mar. 26-8, 2012)