Beam Abort System
2016.6.13
21th SuperKEKB Review
Toshihiro MimashiContents• HER Beam Abort System• Requirements• Design• Components• Beam Abort Kicker Magnets• Extraction Window• Lambertson Magnet and Abort BPM• Ceramic Chamber• Spattering• Kicker Power Supplies• Issues• Whatʼs going on in the case of failure of kicker magnets

Requirements for The Beam Abort System• Beam Abort Gap < 200nsec (KEKB abort gap 500nsec)• (For Stable operation of RF cavities)• Enlarge Horizontal Beam size at the extraction window• (To protect extraction window)• Perfect Beam extraction• All or Nothing

HER Bunch Current Monitors

Beam Abort System

Hardware Components

Abort Kicker Magnets(@7 GeV HER)
Parameters

HorizontalKicker

VerticalKicker

Θ(mrad)2.72(Total)

1.38

B(T)

0.02

0.092

I (kA)

1.2

2.1 (3 Turn)

Length ofFerrite

385 x 8350 x 1# of coils

41Ceramic
Length(mm)500 x 8500 x 1

Extraction Window

H-H

KEKB(LER)SKEKB(HER)

E (GeV)

3.5

7εx (nm)24

4.6

σx(mm)@window

0.68

1.1

Vertical Sweep (mm)1012-15

I (A)

2

2.6

I/σx /δY(A/mm2)

0.3

0.15-0.2

Extraction window Damage Test:
I/σx /δY(A/mm2): 0.53 ⚪️ 0.77 ✖️Monitors for the HER extracted beam
• BPM
1. In front of the dump

• Alumina fluorescent screen
1. In front of the Lambertson
2. In front of the dump

Dump

N.IidaBeam profile measurements
at the “extraction window”

N. Iida, Y.
Enomoto,Y. Suetsugu

An alumina fluorescent screen (Δt=0.2mm), is installedbehind the extraction window.
(The extracted beam profile)
2. The horizontal beam size of single bunch is measured.
σx = 1.18 ± 0.16(mm) Design:1.1(mm)σy = 0.46 ± 0.13(mm)These are included the multiple scattering at thewindow and the thickness of the fluorescent screen.

Horizontal beam size

Vertical beam sizePower Supply (HER)• Common Thyratron switch• Each Horizontal kicker has main
capacitor, saturable inductance andpower crowbar diodes.
Charger＋Thyratron Switch

Saturable
inductance+ Main Capatitance+ Power Crober

Saturable
inductance+ Main Capatitance+ Power Crober

Saturable
inductance+ Main Capatitance+ Power Crober

Saturableinductance+ Main Capatitance+ Power Crober

Main Capacitor+Transformer

Hor. kicker

Hor. kicker

Hor. kicker

Hor. kicker

V kickerHorizontal Kicker current
Saturable
Inductance

200nsec

Power Crowbar
10μsecSaturable
InductancePower Crowbar

200nsec

Ceramic chamber (Water-cool)
Requirements of Ti-coated ceramic chamber：・Penetrate fast kicker magnetic field・Beam image current passes surface of Ti coating・Heating on Kovar Sleeve must be small
100μm Cu Conducting layer coated inner wallof Kovar (ΔT ＜ 20℃@ 2.6A）

Ti Coating Ceramic Chamber with Sputtering
The 500mm long hollow type ceramic which include cooling water path inside

500 mmWhy do we use sputtering for Ti-coating?
・Structural change of chamber decreases acceptable temperature
difference between inside and outside.
・Vapor deposition with Ti wire heating(KEKB) → Sputtering(SKEKB)ΔT < 300-400℃→ ΔT < 100℃

Ti-Thickness Distribution
Ti Thickness [µm]Kapton sheet test
#1
#2
#3
#4

Position [mm]Typical Ti thickness for ceramic chamber#2

Position [mm]Non-uniformity sample

Ti Thickness [µm]Ti Thickness [µm]Good uniformity sample#1#1#2Position [mm]Magnetic Field Response and Chamber Temperature
Magnetic field response with Ti-coating ceramic chamber

ー : CTー : Magnetic field w/o chamber
ー : Magnetic field with chamber

ー : CTー : Magnetic field with chamber
ー : Magnetic field w/o chamberTemperature Rise(Cooling Water)
Beam Current (HER)

LER
KEKB

HER
KEKB

LER
SKEKB

HER
SKEKB

I max

1.6A

1A

3.6A

2.6A

# Bunch

1584

1584

2500

2500

ΔT

2.7

1.4

8.6

2.9 (8.6)

Power

0.56kW

0.29kW

1.8kW

0.6kW
(1.8kW)

New Ceramic

Abort Kicker: New Ceramic Chamber (Spattering)
Injection Kicker: used Ceramic Camber (KEKB)Old CeramicSame Beam Current
But differrent Temperature Rise
(1 Train 1576 Bunches )ΔT(New Chamber)= 3 x ΔT(Used Chamber)IssuesAbort System Failure possibility
Failure Events

What happen in the system

DamageThyratron Break Down

2% of Total Beam loss

No Damage

Gate circuit mulfunction

2% of Total Beam loss

No DamageThyratron misfire

Turn weak Bend magnets

No Damage

Gate circuit misfire

Turn weak Bend magnets

No Damage

H cap break down (charging)

Turn weak Bend magnets

No Damage

V cap break down (charging)

Turn weak Bend magnets

No Damage

Charger fault

Turn weak Bend magnets

No Damage

H cap break down (discharge)

Peak current will be low

Damage ?

H kicker Bias circuit fault

Turn weak Bend magnets

No DamageH kicker Power Crober fault

Turn weak Bend magnets

No Damage

V kicker Cap Break Down (discharge)

No Vertical Sweep

Serious Damage

V kicker Bias circuit fault

No Vertical Sweep

Serious Damage

Vertical Kicker (Pulsed Transformer circuit)
Kicker Current

cap Voltage
BeamExist

Beam Loss at the end of train

Radiation Damage of diode of crowbar
circuit
7mm Pb +200mm Polyechiren +1mm Pb
Reduce 1/10 radiation damage

EndBackup

Layout around the Lambertson
Lambertson

The skew quadrupoles are equipped
at the both sides of Lambertson tocancel the leakage field ofLambertoson Magnet

e+e+

Skew Quad offerrite blockse+Lambertson

Sextupole withskew winding

Lambertson

N. Iida, M. Kikuchi, K. Kodama, T. Mimashi, T. Mori, T. Tawada

The skew quadrupole parmanent magnets tocancel the leakage field from the Lambertson

Ferrite block
Ferrite block
Size: 100 x 25.4 x 150 (mm)B 〜 550 (Gauss)r = 85.5 (mm)→ SK1 = - 7.7e-3 (/m)
which is adjusted the requrement from optics.

Vertical beam size measurement

Y. Ohnishi

Before ferrite installation
After ferrite installation
Targetεy〜20pm

εy〜10pm
εy〜5pm27