LTR, RTL
Commissioning

Measurement of the WS

Requirement from LER

Sector 3

Sector 5

Phase-2

Phase-3gex (µm)

192±22.4

185±28.4< 200< 100gey (µm)

2.01±0.363

1.72±0.704< 40< 15Charge (nC)

w FC

1.4

0.5

4.0

14/Mar/2018
22nd SuperKEKB MAC
N. Iida for the KCG GroupContents
1.

After the DR and RTL commissioning, the beam
was dumped to the east dump at the end of LINAC.

The DR Complex– Positron Damping Ring(DR)– Linac To Ring(LTR) : The injection line of the DR– Ring To Linac(RTL) : The extraction line of the DR

2.

Commissioning of the LTR

3.

Commissioning of the RTL

4.

Conclusion

Sector1

DRThe east dump

The beam shutters were used as beam dump
for the beginning of the LTR and RTL commissioning.

RTLLTR

Sector2

Sector3

Sector4

Sector5

1. DR complex
The DR damps the emittance of the e+ beam to inject into the LER.
The positron beam from Flux Concentrator(FC) has a huge longitudinal distribution.
LTR: The energy spread(5%) should be reduced within the energy acceptance of the DR(1.5%) with theEnergy Compression System(ECS) in the LTR.
RTL: The bunch length extracted from the DR(6.7mm) should be shortened(0.65mm) to fit the LINAC S-band
system with the Bunch Compression System(BCS) in the RTL.
Injection

Extraction

ex(nm)

1300

41.5ey(nm)1200

2.1sz(mm)±30*

6.6sd(%)

±1.5*

0.055

sz=±6.6mm±1.5%

DR design* Full width

ECS
±5%

BCS
Positron Target+FC
sz=±0.65mm

Sector 1

Sector 2

Sector 3

DR Complex

Distributions of the longitudinal phase space atthe entrance and exit of the ECS and the BCS
The energy spread and the bunch length are big compared with the S-band of the ECS and the BCS
Before ECS

After ECSDR

Before BCS

After BCS

sz-sdsz

sd±8mm±30mm±5%±1.5%σz=6.86mm

σδ=0.0573%

σz=1.33mm
σz=0.645mm

σδ=0.801%

DR Complex

Parameters of the ECS and the BCSECSBCS

Before ECS

After ECS

Before BCS

After BCS

Wisth of z

W=±8mm±30mm

σz=6.6mm

σz=1.3mm

Width of d

W=±5%±1.5%

σd=0.055%

σd=0.80%

R56 [m]- 0.61- 1.05

Vc [MV]

4121.5

DR Complex

Site of the DR

Entrance of the LER

DR SiteKEK Site〜30m

The energy tail can be
cut up to 20% of thecharge by thecollimators at the LTR in
LINAC region beforeloss in the DR.

Because the borderline of KEK is close, the beam loss outside of LINAC should be low.

2. Commissioning of the LTR–

The initial commissioning of the LTR started on Jan. 23rd.
–

The beam was reached to the end of the LTR on Jan. 24th .

–The charge from LINAC was 0.75nC/bunch without the FC.

–

The beam loss outside of LINAC should be low because the borderline of KEK is close.

–

The R56 of the 1st arc and an accelerating structure consist the Energy Compression System(ECS).
–

The energy spread (sd) of the injection beam to the DR should be smaller than the energy acceptance,±1.5%.
The entrance of the DR–

The ECS compresses sd from ±5% to ±1.5%.

–

The 4 collimators cut the low energy tail in the LTR.

–

The magnets of the LTR and the RTL are set at the energy of the DR.

±1.5%

Commissioning of the LTRbx, byLTR Optics Plothx

ECS

Beam Dump(Beam shutter 2)

The beamshutter is used
as a beam dump
for the LTR
commissioning.

Beam Dump(Beam shutter 2)

MSCN9MSCN8

R56=-0.61sx, sy
２セクター

Accelerator
Structures

SY2

MSCN7Accelerator
Structures

QF QD

MSCN6

SY24 Collimstors
COL4cut the energy COL1 COL3
COL2
tail in SY2BEND
STEERING
ACCe+

Sector ２

MSCN5

MSCN4Sector ３

Commissioning of the LTR

Tuning of the LTR

1. We made the ”core beam” to adjust so that the centers of beam energy and dz pass through the center of beam pipes.
In this time, the core beam was made by lowering the energy of the beam and cutting deeply the tail of energy with the collimators.

–2. The zero crossing of the ECS was scanned by using the core beam.
3. Finally, the energy of the beam was increased and the energy tail under -5% was cut with the collimators.
Screen M.
at hx=0.7m

The core beam should pass the center of beam pipes.

Core Beam(1) Entrance of LTR
dOperation Beam

− 5%(3) Exit of the ECS(2) Exit of the 1st Arcdd

The operation beam rotates around the center of beam pipes.

±1.5%

±5%
ddDR

Commissioning of the LTR

ECS Tuning
We searched the zero-crossing
phase of ECSZero Crossing of ECS accelerator

Cut byCollimators

Energy Acceptance of LTR (±5%)

Y. Seimiya, N. Iida

Commissioning of the LTR Energy Spread is checked by the ECS ON/OFFShift report “2018_01_24_17_NakamuraS_EnomotoS.pptx”

on the screen monitor in the 2nd arc of the LTRECS ON127deg

ECS OFFddzz

yx

The beam size corresponding toenergy spread is smaller properly.

ECS ONphase 307deg

Opposite PhasedVcdz

The energy spread is larger than that of ECS OFF.

z

By the way,

In the case of the core beam,
the energy spreads looks same in the three cases.
ECS OnECS Off

ECS Oppositephase

The core beam is independent on the ECS phase.

Commissioning of the LTR

N. Iida, F Miyahara, Y. Yano, and Y. Ohnishi

Measurements with the Wire Scanners in the LTR w/wo FC
The wire scanner system has four wire scanners(A, B, C, D) in one region.
FCStbA

FC
Acc
5kVC

A

C
X

X

Y

B

X

Y

B
X

X

Y

X

Y

Y

DX

Y

DX

Y

FC : Stand-by

FC : 5kVgex [µm]

245.5

288.5

gey [µm]

241.8

255.8

BMAGx

1.58

1.00

BMAGy1.53

1.01

Y

No change was observed with FC
Off and On.

Loss Monitors
FC OFFFC ON
H. Ikeda

Loss Monitors

T. Kobayashi
Arc Sensersof RF sustem

The signals of both of loss monitors and arc sensers of RF system are small enough.

Commissioning of the LTR

Tuning items of the LTR
LTR Study

Responsibles

1.

Dispersion Fine Tuning

Y. Seimiya, N. Iida

2.

3-BPM measurement

T. Ishibashi, H. Sugimoto3.

Local Bump Study

Y. Ohnishi, R. Ueki

4.

Parameter Matching (Wire Scanner)

N. Iida, Y. Ohnishi, Y. Yano

5.

QuadBPM (Beam Based Alignment)

H. Sugimura, H. Sugimoto

6.

ECS Fine Tuning

Y. Seimiya, N. Iida

Tuning of ECS Pulse Timing

LINAC Operator

Single kick response measurement

M. Kikuchi

7.

Many new rookies (more than 11) joined the commissioning of the LTR.

Commissioning of the LTR

Many basic beam studies have been done.
Dispersion correction

Y. Seimiya

Local-bump
Y. Ohnishi

3-BPM

T. Ishibashi

QuadBPM

H. Sugimura

Single kick response measurement

M. Kikuchi

3. Commissioning of the RTL
1.

The DR Commissioning started on Feb. 8th.
–The RTL commissioning was immediately done, and the bunch compressed beam reached to the east
dump of LINAC in Feb. 10th .

2.

BCS Tuning <- Done

3.

Dispersion measurement and correction–

1st arc <- Not yet––4.

Sector 3

for the injection kicker trouble and the reduction of electric power due to the trouble of discharge.

2nd arc <- Done very well

Emittance measurement with wire scanners at the LINAC–

Sector 3–

Sector 5

Sector 4

Sector 5

Commissioning of the RTL
Y. Seimiya

The BCS Tuning

1st Arc

1.

The orbits were corrected without the accelerating structure.

2.

The zero crossing phase of the BCS was found.

3.

The accelerating phase of the sector 3-5 was searched.

4.

The BCS phase was checked at the east dump. BCSe+– 0 or p ?

RTL Optics
2nd arc with
R56=-1.05
Accelerating structure

AcceleratingstructureCheck the BCS Phase

Green line: True phaseof the BCS (347.7°)
The energy spread is small.

Sector 3 - 5

Screen monitor(YAG) in front of the east dump

Blue line: The opposite phaseof the BCS (167.6°)
Y. Seimiya

Return charge to the LINAC
Y. EnomitoThe charge returned from the RTL is almost same as that going to the LTR.
Even if the energy tail will be cut severly (20% in the maximum situation) ,the charge is enough for the Phase-2.

Commissioning of the RTL

RTL
2nd Arc

Dispersion correction of the 2nd arc
Y. Seimiya

The beam energy was changed by shifting the BCS phase.

Sector3-5

Sector3-5

Sector3-5

Before Correction

After Correction<hx> [mm]7919<hy> [mm]

9.4

7.7

The leak of the horizontal dispersion decreased by a quarter.
The Fudge Factor of the quads in the 2nd arc is 0.955.

Emittance Measurementwith the Wire Scanners in Sector 3

Commissioning of the RTL

Emittance before and after the dispersion correction was measured by the WS in the sector 3
Before dispersion correction

After dispersion correction

AACXXYBCDY

B

Sector 3

DDR(Optics Calculation)

Before correction

After correctiongex (µm)

293±44.5192±22.4

63.9

gey (µm)

1.84±0.163

2.01±0.363

XY-coupling<=3.15±0.57%

The horizontal emittance is decreased 2/3.

The XY-coupling is estimated as less than 3.15%.

Commissioning of the RTL

Emittance Measurementwith the Wire Scanners in Sector 5ACX

BMeasurement of WSRequirement from LER

Sector 3Sector 5

Phase-2

Phase-3gex (µm)

192±22.4

185±28.4< 200< 100gey (µm)

2.01±0.363

1.72±0.704< 40< 15YD• No emittance growth is observed with 0.75nC e+
beam between sector 3 and sector 5.
• The horizontal emittance satisfies the requrement ofthe Phase-2 but not Phase-3 yet.

Commissioning of the RTL

Dispersion measurement of the DR
H. SugimotoH [m]X

6.08e-5Y

4.49e-5d5.5e-4

De[m]

e [m]

De/e

1.84e-1129.7e-9 (from DR Optics calculation)

6.2e-41.36e-11

9.3e-10 (from WS measurement)

1.5e-3The increments of emittancefrom the dispersions at theextraction point affect negligibly
small to the emittance growth.

The source of the remaining horizontal emittance grouth is the dispersion leak from the 1st arc.

List to do
1.

The orbit feedbacks should be worked at,–the entrance of the LTR–

the end of the LTR–

the upstream of the 2nd arc of the RTL

2.

Dispersion correction of the 1st arc in the RTL–

By changing the beam energy of the DR–Emittance measurement with the wire scanner at the sector 3 and 5

3.

Bunch length measurement with the streak camera at the sector 34.

Energy spread measurement with the screen monitor(YAG) at the end of LINAC or with thewire scanner at the beam transport line of the LER.
–Requarement : 3s<0.5%

5.

The beam based alignment should be done for the remained BPMs.

6.

The bunch charge measurements with BPMs of LTR and RTL should be corrected.

Conclusion– The first commissioning of the LTR, DR, and RTL were succesfully done.
– The LTR commissioning– The beam tuning is almost done

– The RTL commissioning– The emitttances satisfy the requirements of the Phase-2 but not Phase-3.
– The dispersion of the 1st arc should be corrected during the Phase-2.

Thank you for listening.

BackupM. Kikuchi,
H. Sugimoto

(1s)
(1s)

BCS Optimization– Vc of BCS– Actually, we optimized more Vc of BCS to be small energy spread at theentrance of main ring, because we have one more ECS after LINAC and thebeam transport line with large R56.
After BCS

V=18.4MV

V=21.5MV

Entrance of Main Ring

Schedule of LTR Commissioning
The beam passed to the end of LTR and is roughly tuned in two days !

doneplanned

How tuning ?
1.

Making core beam
– The beam is cut by the collimators at the 1st arc, and the energy is fixed.
– The “choice beam” should pass the center of the orbit of the LTR.
– The phase of the accelerating structure of the ECS should be fixed to the zerocrossing with the “core beam”.
– The energy of the 2nd arc is fit to the “core beam”

2.

The injection tunings are done with the “core beam”

Choice beam d− 5%(3) Exit of the ECS Entrance of the DR(2) Exit of the 1st arc(1) Entrance of LTRdd

The choice beam always pass the center of the design orbit.

How tuning ?
3.

Shift to the operation beam
– Shift the beam energy up to 5%– The lower energy tail (- 5%) is cut by the collimators.
– The phase of the ECS should NOT be moved.
The core beam always pass the center of the design orbit.

Core beamd− 5%(3) Exit of the ECS Entrance of the DR(2) Exit of the 1st arc(1) Entrance of LTR

dd

The operation beam rotates around the center of beam pipes.

Operation beam

±1.5%±5%dd

Y. Seimiya

LTR Dispersion correction34

Y. Seimiya

Dispersion Correction（SP464）
BeforeAfterWire Scanner測定（３セクター）補正前後
補正前

補正後

Wire Scanner測定（５セクター）補正後

Wire Scanner測定（５セクター）補正後

３セクター

５セクター

gex (µm)

192±22.4

185±28.4

gey (µm)

2.01±0.363

1.72±0.704

３〜５セクターで、e+(0.75nC)のエミッタンス増大は観測されない。

Expected value of the RMS of a wire
The expected value of the RMS of a wire with radius “a” can be written as follows;ydS = a 2 − x 2 dx

axarrms =∫ xxtrue =−a2a 2 − x 2 dx

π a22p2meas=2rrms

a2F. MiyaharaDispersion leak does not appear
downstream of the BCS=<hx>=9.4mm<hy>=28.1mm<hx>=19mm<hy>=7.7mm

Even if the dispersions leak to the RTL, after BCS, the energy conponents rotate to the bunch length.

Injection/Extraction kickers and septa