Status of Damping ring, beamtransport line
20th KEKB ARC
M. Tawada
2015.02.24

1Contents• ConstrucFon status of DR• Status report of DR &BT component– Field measurements for DR magnet– DR Kicker– HER Septum magnet– Remodeling of HER septum power supply– Schedule for the new injecFon component• DR install schedule & commissioning plan
• Summary‐ Vacuum, RF and monitor of DR were presented byShibata‐san, Kobayashi‐san and Ikeda‐san, respecFvely.
2Damping Ring•••••

DR is newly constructed at the end of Sector‐2 of the Linac.
The positron beam of 1.1 GeV is injected into the DR.
ASer circulaFng in the DR for 40 ms, the damped beam is injected back into theLINAC.
LTR line with the energy compression system (ECS) is incorporated.
RTL line with bunch compression system (BCS) is incorporated.

3

DR Beam transport lines (LTR & RTL)
• Magnet installaFon was almost completed for the beam transport lines.
• Power cables between PS and magnets were installed.
• Monitor cables also installed.
LTRRTL4

Damping Ring••••

Cable racks were installed in the power supply building.
Power cables for magnets were installed.
All power supplies for the magnets were delivered. (except for steerings.)
Ready for installaFon of the beam line components.

DR‐NorthDR‐SouthPower supply building5

Status of DR & BT components

6Field measurement for DR magnet
K. Harada & T. Ueda
• Mass‐measurements for B1‐B4, QRD, QRF, Sx were completed.
• Due to the trouble with harmonic coil, mass‐measurement for QF/QD/QS wasdelayed.
• End shim correcFons are needed for QF/QD/QS . But it will be completed unFlJune 2015.
MagnetNo.

Mass‐measurement

B1

33

completedB2

39

completedB3

5completedB45completed

QF/QD/
QS

52+26+1+1

Not yetQRD

7+1

completed

QRF

3+1

completed

Sx

74+2

completed7

BL measured by long ﬂip coil
(B1 & B2 dipole magnet)
B1

B1

B1

B2

B2

B28

DR Inj. & Ext. Kicker• DR has 2 trains, which are separated about 100ns and 2bunches per train, which areseparated 96 ns.
• DR kicker has to inject or extract 2 bunches per pulse .
• Rise Fme and fall Fme must be < 100ns.
• 2 kicker magnets for injecFon and extracFon, respecFvely.
Inj. kicker

Inj. Septum

LTRDR Kicker
Total deﬂecFon angle (mrad)5.2(inj.)
4.7 (Ext)

No. of bunch /pulse

2

Bunch space (ns)96

Rise Fme (ns)<~100

Fall Fme (ns)<~100Stability<1% (Inj.)<0.1% (Ext.)

Max. repeFFon (Hz)50

RTL
Ext. kicker

Ext. Septum9DR Inj. & Ext. Kicker•DR kicker are designed as an inducFve (lumped) type kicker.

•Inj. and ext. kicker are same design.

•Pulse shape : double half‐sine. (Two half‐sine pulses are overlapped each other.)•Pre‐pulse and tail noise should be < 5%.

•

Bunch feedback system is indispensable to compensate the pre‐pulse and tail noise kick.

Saturable inductance~100ns 96ns ~100ns 96ns

<5%

<5%
10

DR Inj. & Ext. Kicker
X：100ns/div
Y:500A/div
I=1700Ap‐‐‐→Pre Pulse ‐100ns
75.6A
4.4%

•
•
X：100ns/div
Y:50A/div•TypelumpedPulse shape

Double half‐sine

Pulse width (ns)300

Length (mm)240

Aperture (mm)82(H) x 53 (V)Mag. Inductance (uH)0.8

Bmax (T)0.04Max Current (A)1710 (Inj.)
1550 (Ext.)

Jiher (ns)

< ±9 (Inj.)< ±2 (ext)

In order to achieve short rise Fme, a saturable
inductance is used.
Command charger is used to achieve the requiredstability.
Because of severe jiher requirements, DC PS areused for the cathode’s and reservoir’s heater of
the thyratrons.
11

DR Inj. & Ext. Kicker
Issues:• MinimizaFon of pre‐pulse and tail noise.
• RadiaFon hardness problem.
⇒RadiaFon shields for the magneFc switch areneeded.
• Timing jiher.
• At ﬁrst we use thyratron tube and we plan
to replace it with solid‐state switch later.
• Ceramic duct with Ti coaFng.
• InstallaFon to DR tunnel.

Inj. kicker

Ext. kicker

12

Prototype septum magnet trouble T. MoriIn‐vacuum septum
Cracked coil••

Coil of prototype septum was broken with 1‐hour operaFon with 50Hz.
The reason is not clear.
––•

Conductor size: 6x6‐□3⇒6x8‐φ4––•

Damaged coil?
Metal faFgue phenomenon by the coil vibraFon?
We have tested with 6x8 coil for >20 hours operaFon with the prototype magnet.
⇒ No problem. So, we conFnue to fabricate the producFon magnets.

No. of coil hook: 9 (prototype magnet) ⇒ 17 (producFon magnet)–Stress for the coil can be expected to be reduced t o 1/4.

13

Shim Shape for Septum CoreT. Mori

Septum end

3 shims
H=0.08, w=1.0, wtaper=2.0
H=0.06, w=1.0, wtaper=2.0
H=0.1, w=0.5, wtaper=2.0

Shim shape for producFon magnet was
opFmized to meet the requirements.

Septum ﬁelds calculated

14

HER Septum Chamber DesignT. Mori & K. Kanazawa
Septum‐3Septum‐3No changesSeptum‐2Septum‐1

Very Fght
KEKB HER Septum ChamberSuperKEKB HER Septum Chamber

2.6m

2‐septum in 1‐chamber

15

Stability improvement of septum PS
Because stability of KEKB septum PS was not so good, operator had to adjust it
frequently.
• Improve the stability of charging voltage.
••••

Make the voltage monitor’s response faster.
Replace the charger using thyristor to that using switching power supply.
Control charging Fming by replacing diode to thyristor.

•Introduce high precision auxiliary charger.

⇒ Stability<±1E‐4 for 4 hours was achieved.

Start
±1E‐4

Aux. P.S.
4hour later

Issue:
During remodeling these PS, we found many parts, which are fabricated in KEKB were broken.
We need to repair these parts unFl the SuperKEKB operaFon.

±1E‐416

19th KEKB ARC RecommendaFons:
Setup a solid schedule for the new injecFon components to be consistent with the DRschedule and meets the Phase II and Phase III milestones.

Schedule for the new injecFon components

Reply:• HER Septum & HER Abort Kicker
components will be fabricated unFl thissummer.
• LER Septum, LER abort kicker compoentsmust be fabricated in FY2015. And thesewill be installed between Phase‐1 andPhase‐2.
• FabricaFon of pulsed magnets and PS for
DR will be completed in this ﬁscal year.

17

19th KEKB ARC RecommendaFons:
In order to complete the Damping Ring commissioning during a one‐month period, aprecise commissioning plan needs to be prepared with detailed procedures and decision
trees and suﬃcient commissioning staﬀ idenFﬁed.

DRSchedule & Commissioning Plan

18

M.Kikuchi(2014.11.6)
The Fme span between Phase‐Iand Phase‐II is 10 months.
DR beam‐commisioning can bestarted on LINAC beam mode
just before Phase‐II.

Damping ring
ConstrucFon schedule

M. Kikuchi

DR Commissioning will
start before Phase‐2.

InstallaFon work conFnues inFY2015‐2016.
19

PrecauFons for DR commissioning

N. Iida• LTR InjecFon– The power supply of injecFon kickers are locatedin DR tunnel.
• The LTR beam tuning should be done in the state whichsome screen monitors at the end of LTR are put in.

• Night‐Fme– For example, 1:00 – 9:00
– LINAC tuning– When the beam tuning of DR is over, vacuumscrubbing can be done.
• DR needs about 2 [A.Hr].
20

DR beam commissioning plan

N. Iida>10 weeks for DR commissioning will be needed.

21

19th KEKB ARC RecommendaFons:
The beam in the Damping Ring (DR) needs to be aborted when the SuperKEKB rings
abort their beams. The locaFon and design of this DR abort system needs to be ﬁnalized
and constructed to be ready for high current operaFon of SuperKEKB.
N. IidaDR beam extracFon
due to the LER abortRTL

Beam shuher

When the LER beam is aborted,
1) Close the beam gate.
2) Close the beam shuher atthe end of RTL.
3) ASer conﬁrming the beamshuher closed, theextracFon kicker of DR ﬁres.

22Summary– DR•The DR tunnel is ready for installaFon of the beam line components of the DR.

•InstallaFon work for DR will conFnue in FY2015 and FY2016.

•DR commissioning will start before Phase‐2 and needs > 10 weeks.

– HER & LER•New injecFon components for HER will be fabricated unFl this summer andwill be installed by the end of this autumn.

•To check the reliability, we must have a long term operaFon of the producFon
septum magnet before the installaFon.

•Many parts of Septum PS were broken and must be repaired unFl SuperKEKB
operaFon.

23

Backup24

DR Inj. & Ext kicker
R&D transmission kicker• Transmission kicker shows a beher performance of rise Fme.
• R&D for transmission kicker (SLC type, i.e. out‐vacuum moldedtype) are being performed.
• We need more Fme to develop it.

25

DR inj. & Ext. Septum
Inj.

Ext

DeﬂecFon angle(mrad)

80

103

No.

1

1Field strength (T)

0.36

0.47

TypeEddy‐current

Eddy‐current

Aperture (mm)70(H)x24(V)

70(H)x30(V)No. of coil turns

11Septum thickness
(mm)

2.5

2.5

Waveform

Full‐sine

Full‐sine

Pulse width (μs)

300

300

Peak Current (A)

8000

12500

Max rep. (Hz)50

50

Stability

<1E‐3

<1E‐4

In‐vacuum

Out‐vacuum
w/ ceramic duct

DR inj. Septum PS

DR Ext. Septum mag.

• No. of coil turns for DR ext. septum was changed
2 ‐> 1 to make the structure simple.
26

Tracking through Septum Field

Scaled to makethose averages the same

Septum ﬁeldOrbit• Septum ﬁelds calculated with 3 kinds of shims– ℎ=0.08, 0.06, 𝑤=1.0, ​𝑤↓taper =2.0
– ℎ=0.1, 𝑤=0.5, ​𝑤↓taper =2.0

• Tracking with ±2.5​𝜎↓𝑥 width beam with same momenta
27

DistorFon of InjecFon Beam

Angular diﬀerenceDistorFon of injecFon beam through ﬁnal septum•[𝜇rad]；~5% distorFon•

2.5×√⁠​𝜀↓𝑥 /​𝛽↓𝑥 =24.4

Divergence angle of injecFon beam：

No big diﬀerence between ﬁelds with 3 shimsℎ=0.08 is adopted; but tolerance is 20𝜇m ⇒ℎ=​0.08↓−0.03↑+0.0128