Limits of MA cavity C. Ohmori KEK. What kind of limit? Voltage Field Gradient Temperature (cooling)...

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Limits of MA cavity C. Ohmori KEK

Transcript of Limits of MA cavity C. Ohmori KEK. What kind of limit? Voltage Field Gradient Temperature (cooling)...

Page 1: Limits of MA cavity C. Ohmori KEK. What kind of limit? Voltage Field Gradient Temperature (cooling) –below 200 deg. C for long term (Hitachi Metal Co.).

Limits of MA cavity

C. Ohmori KEK

Page 2: Limits of MA cavity C. Ohmori KEK. What kind of limit? Voltage Field Gradient Temperature (cooling) –below 200 deg. C for long term (Hitachi Metal Co.).

What kind of limit?• Voltage• Field Gradient• Temperature (cooling)

– below 200 deg. C for long term (Hitachi Metal Co.).

• Frequency• Environments• Materials

• But, these are not independent !– Low duty-High voltage vs High duty-Medium voltage

Page 3: Limits of MA cavity C. Ohmori KEK. What kind of limit? Voltage Field Gradient Temperature (cooling) –below 200 deg. C for long term (Hitachi Metal Co.).

Magnetic Cores for Cavity

1.00E+09

1.00E+10

1.00E+11

1 10 100 1000 10000

Brf[Gauss]

up'Qf

Magnetic Alloys

Ferrites

Requirements for PRISMB=V/S=400Gauss

Page 4: Limits of MA cavity C. Ohmori KEK. What kind of limit? Voltage Field Gradient Temperature (cooling) –below 200 deg. C for long term (Hitachi Metal Co.).

PRISM Cavity Design

.

APS

AMP

Cavity

By C. Ohmori, Y. medium

Beam Pipe

Side View

33cm

Page 5: Limits of MA cavity C. Ohmori KEK. What kind of limit? Voltage Field Gradient Temperature (cooling) –below 200 deg. C for long term (Hitachi Metal Co.).

RF CavitiesField Gradient of Cavities for Proton

Synchrotrons Proton Synchrotron RF System

0

10

20

30

40

50

60

0 2 4 6 8 10 12

Frequency (MHz)

Field Gradient (kV/m)

SATUNE

MIMAS

CERN PSB

CERN PS

AGS

ISIS

KEK BSTR

KEK PS

JKJÅ@50GeV MR

JKJ Å@3GeV RCS

50GeV MR Upgrade

KEK-HGC

Ferrite Cavities

JKJ RF CavitiesKEK-PS MA Cavity

Proton Synchrotron RF System

0

50

100

150

200

250

0 2 4 6 8 10 12

Frequency (MHz)

Field Gradient (kV/m)

SATUNE

MIMAS

CERN PSB

CERN PS

AGS

ISIS

KEK BSTR

KEK PS

JKJÅ@50GeV MRJKJ Å@3GeV RCS 50GeV MR UpgradeKEK-HGC

PRISM

High Gap Voltage (X 3) & Short Cavity (X 2)Very High Gradient for very short moment (10s) !

Page 6: Limits of MA cavity C. Ohmori KEK. What kind of limit? Voltage Field Gradient Temperature (cooling) –below 200 deg. C for long term (Hitachi Metal Co.).

RF system R&D

• 43 kVp/gap using 700 test MA cavity:

• Equivalent to 150kV/m seems possible by 33 cm-MA cavity at 5 MHz

• Design goal (60 A RF current) of AMP was achieved.

• Very compact design for AMP and APS.

RF voltage at the gap (red line)

Page 7: Limits of MA cavity C. Ohmori KEK. What kind of limit? Voltage Field Gradient Temperature (cooling) –below 200 deg. C for long term (Hitachi Metal Co.).

Limit for High Field GradientSo far, up to 2 kG, we have tested for Brf.Insulation using SiO2 can stand few volts.

(1 volt/20 m=50kV/m in transverse direction.)

For PRISM operation (0.1% duty), 150 kV/m seems acceptable.1%-duty seems acceptable by the forced-air cooling.

Power amplifier and driving scheme give another boundary.

At 5 MHz, Qf=7x10^9. But, it will be more than 10^10 at 10MHz.RIKEN reports that MA can be used at 20 MHz and higher Qf.

More field gradient at higher frequency ?

But, MA is affected by outer magnetic field. Few hundreds gauss seems dangerous from the experience of 150 MeV FFAG.

Page 8: Limits of MA cavity C. Ohmori KEK. What kind of limit? Voltage Field Gradient Temperature (cooling) –below 200 deg. C for long term (Hitachi Metal Co.).

Limits for high duty operation• Cooling of MA cores is main issue.• But, reduction of impedance happens by

environmental conditions (capacitance and magnetic field)

• Cooling schemes– Air KEK-PSBooster

– Indirect water 150 MeV FFAG

– Direct Water cooling J-PARC, CERN-LEIR

Page 9: Limits of MA cavity C. Ohmori KEK. What kind of limit? Voltage Field Gradient Temperature (cooling) –below 200 deg. C for long term (Hitachi Metal Co.).

Forced Air cooling• At KEK-PS booster, ferrite cavities have been

replaced by MA cavities.– 20 Hz, 40-500 MeV– 30-40 kV– Duty : 25-30%– Impedance ?– Power dissipation ?

• Pop FFAG uses air cooling.

Page 10: Limits of MA cavity C. Ohmori KEK. What kind of limit? Voltage Field Gradient Temperature (cooling) –below 200 deg. C for long term (Hitachi Metal Co.).
Page 11: Limits of MA cavity C. Ohmori KEK. What kind of limit? Voltage Field Gradient Temperature (cooling) –below 200 deg. C for long term (Hitachi Metal Co.).

Indirect Cooling• J-PARC R&D shows 5 kW/core (80 cm OD) seems

acceptable without significant impedance reduction. – But, 5kW is not enough for J-PARC– Conflict between cooling efficiency and impedance.

• 150 MeV FFAG can be operated with 25-50 Hz repetition. Cavity impedance is reduced by the magnetic field.

• FNAL MA cavity• New HIMAC MA cavity (Toshiba core)• Saclay

• Possible to use at high frequency if you design carefully.

Page 12: Limits of MA cavity C. Ohmori KEK. What kind of limit? Voltage Field Gradient Temperature (cooling) –below 200 deg. C for long term (Hitachi Metal Co.).

FNAL

J-PARCR&D

Page 13: Limits of MA cavity C. Ohmori KEK. What kind of limit? Voltage Field Gradient Temperature (cooling) –below 200 deg. C for long term (Hitachi Metal Co.).

Direct water cooling• Put cores in the water jacket.

– J-PARC, COSY, CERN-LEIR

• J-PARC Cores are coated by epoxy with 0.2 mm thickness. • Three different core configurations

– Non cut core: 50-60 kW/6 cores X 300 H– Cut core (medium Q): 50-60 kW/6 cores X 150 H– By combination of non-cut and med-Q, hybrid cavity for RCS– Cut core (high Q): 50-80 kW/6 cores X 100 H for MR– Requirements : 45 kW for non-cut and mid-Q, 50- kW for high Q.– Not much impedance reduction by water below 3 MHz. But, not

higher than 4 MHz because of capacitance by water

Page 14: Limits of MA cavity C. Ohmori KEK. What kind of limit? Voltage Field Gradient Temperature (cooling) –below 200 deg. C for long term (Hitachi Metal Co.).

Capacitance effects by water

Direct Cooling Indirect Water Cooling

Page 15: Limits of MA cavity C. Ohmori KEK. What kind of limit? Voltage Field Gradient Temperature (cooling) –below 200 deg. C for long term (Hitachi Metal Co.).
Page 16: Limits of MA cavity C. Ohmori KEK. What kind of limit? Voltage Field Gradient Temperature (cooling) –below 200 deg. C for long term (Hitachi Metal Co.).
Page 17: Limits of MA cavity C. Ohmori KEK. What kind of limit? Voltage Field Gradient Temperature (cooling) –below 200 deg. C for long term (Hitachi Metal Co.).
Page 18: Limits of MA cavity C. Ohmori KEK. What kind of limit? Voltage Field Gradient Temperature (cooling) –below 200 deg. C for long term (Hitachi Metal Co.).

J=PARC RCS Tunnel

Page 19: Limits of MA cavity C. Ohmori KEK. What kind of limit? Voltage Field Gradient Temperature (cooling) –below 200 deg. C for long term (Hitachi Metal Co.).

CERN-LEIR   Cavity ( 2005/4 )