report from rf session (1:30-5:40 pm, 3/30/2004) h. haseroth and derun li center for beam physics...

Report from RF Session Report from RF Session (1:30-5:40 PM, 3/30/2004)(1:30-5:40 PM, 3/30/2004)

H. Haseroth and Derun Li

Center for Beam PhysicsLawrence Berkeley National Laboratory

MICE Collaboration Meeting at CERNMarch 31, 2004

MICE Collaboration Mgt in CERNMarch 31, 2004

Report from RF Session Derun Li

Center for Beam Physics LBNL

MICE RF

• Eight 201.25 MHz cavities (4-cavity per module) with curved Be windows (21-cm radius and 0.38 mm thick)– Cavity body, ports, vacuum, probe, cooling channel– RF windows + couplers– Curved Be windows

• 8 MW (or more?) peak RF power system + distribution system – Low level RF control (RAL)– Driver amplifiers, amplifiers and PSs– Distribution system (rigid coaxial transmission lines,

pressurization with dry N2 or SF6), hybrids vs circulators, phase shifters, …




Agenda

Status of the 200 MHz cavity (D. Li) Status of power amplifiers and drivers at RAL (P. Drumm) 201 MHz cavity fabrication (R. Rimmer) Status of power amplifiers and drivers at CERN

(H. Haseroth) Curved Be window designs (S. Yang) 201 MHz RF system for MICE (hybrids) (Al Moretti) Controls (Blondel’s table) Layout Layout Discussions

MICE RF - Power sources and distribution system

(PD, HH and AM’s presentations)

RF group at the Daresbury SRS

• Mike Dykes (group leader)

• Andy Moss (senior RF Engineer)

• plus two more

• MD & AM are here…




Baseline ?

4 MW Transmitter2 MW Transmitter 2 MW Transmitter

Master Oscillator

201 MHz Cavity Module 201 MHz Cavity Module

3 db Hybrid & Load

Matched Splitter

Circulator & Load




Split – Circulator - RF Scheme

R.F.LEVEL

R.F. LEVEL SUM

CIRCULATOR

CIRCULATOR

PHASE

SHIFTER

R.F. SOURCE33kV H.T. 18kV H.T.

TUNE ERROR

TUNE ERROR

CAVITY PHASE

PHASE DET

PHASE DET

TH116

2.5MW

4616

250kW

SOLID STATE DRIVER

R.F. LEVEL

AND

PHASE

CONTROL

CAVITY PHASE

F R

F R

70db COUPLER

70db COUPLER

MATCHED

POWER

SPLITTER

CAVITY

CAVITY

LOAD

LOAD




RF Power Baseline Design

8 MW peak RF power:

• RF Power Design driven by cost issues (no funds for a new system)– Optimal – one amplifier per cavity

• Two amplifiers from LBNL = 4 MW total

• One or two amplifiers from CERN = 4 MW total– If 1 amplifier – needs a bigger drive?– Possibly more coaxial components from CERN

• Spare TH116 Tubes from ISIS

• Low level RF and RF layout (not covered this time)




RF Power Amplifiers available at CERN/PS

There is one more amplifier from Linac1: It got modified to 88 MHz (foreseen for tests with our 88 MHz cavity for the cooling channel in the CERN scenario. 2 MW(FTH triode tube)driver (LHC type, modified) available If amplifier is modified: 4 MW achievable, but driver must be pushed

Of course: to modify to 88 MHz and modify again is not too attractive…




RF driver Amplifiers available at CERN/PS

200 MHz: 3 amplifiers 350 (400) kW, one available now, 2 more in the near future(with Siemens tube no longer built). Still several spare tubes in stock. One tube good for up to 15 000 h in300s, 1 Hz, not full power regime.

Needs power supply for 40 kCHF. Switching via cathode (5 kCHF).

GSI (Hutter) says that change to a tube which is still available is not a major issue…




RF Power and Distribution (1)

• Hybrids versus circulators– Helpful discussions – Issues become clearer – Should come to an agreement soon

• RF experience from two communities: (reflection & isolation of RF power – protection of components)

Synchrotron/storage ring LinacsOptions: circulators hybridsCosts expensive cheaperReliability + √Source klystrons triodes

Operation mode 99% for users ……

• A reasonable choice for MICE: hybrids




RF Power and Distribution (2)

• Rigid 50 Ω, 4 1/16”- 9 3/16” coaxial transmission lines with pressurized gas – SF6 gives higher P/P’ ratio, but have safety issues – Dry N2 at ~ 2 atm absolute pressure

Cost of the Components (by AM): The cost of components assuming 25 feet of 9 3/16 straight and 4 EL-Bows and 25 feet of straight 6 1/8 and 4 EL-Bows

25 feet ST 9 3/16 line $5,60025 feet ST 6 1/8 line $3,7004 EL-Bows 9 3/16 $10,3004 EL-Bows 6 1/8 $6,800The first Hybrid $8,000Second Hybrid $4,500First Hybrid Load $2,022Second Hybrid Load $1,400Mech. Phase Shifter $4,300Several directional C $4,500Total Cost = $49,722




Main power consumption and cooling requirements for 1 Hz and 1 ms pulse length:

2 4 MW rf require about 2 10 MW supply.

Total: 20 kW with 0.1% duty cycle.

Filament needs 2 360 A and 15 V = 2 5 kW = 10 kW.

Total for final amplifiers: 30 kW

Total for driver amplifiers: 10 kW

Grand Total for rf amplifiers: 40 kW

50 % of power estimated to go into the cooling water: requires about 20 l/min water.

The rest goes into the air…

Available coax lines (9 inch?): 10 cubes for making 90 bends.

Power Consumption (HH)

The 201.25 MHz Cavity with Be windows

- Prototype(DL,RR,SY)




Status

The 201 MHz cavity design and fabrication go smoothly Spun shells ready for machining after e-beam welding Nose pieces, stiffener rings and fixture were made Support structures for the equator welding Ready for equator welding tomorrow at JLab

Engineering design (details) is still continuing Ports (succeeded in extruding tests and qualified the

techniques) Couplers (done with conceptual design) Tuners

Significant progress on curved window design and fabrication– Succeeded in making S.S. curved windows, curved Be windows

for 805 MHz cavity by Brush-Wellman company– Ready for 201 MHz cavity windows

The cavity will be ready for test at MTA, Fermilab this fall !




The Cavity Profile update

De-mountable Pre-curved Be windows to terminate RF fields at the iris

2o tilt angle

Spherical section at the equator to ease addition of ports (± ~ 6o)Elliptical-like (two circles) nose to reduce peak surface field

6-mm Cu sheet allows for uses ofspinning technique and mechanical tuners

Stiffener ring




The Cavity Parameters

The cavity design parameters The cavity design parameters – Frequency: 201.25 MHzFrequency: 201.25 MHz– ββ = 0.87 = 0.87– Shunt impedance (VShunt impedance (VTT

22/P): ~ 22 MΩ/m/P): ~ 22 MΩ/m– Quality factor (QQuality factor (Q00): ~ 53,000): ~ 53,000– Curved Be window radius and thickness: 21-cm and 0.38-Curved Be window radius and thickness: 21-cm and 0.38-

mmmm

Nominal parameters for cooling channels in a muon collider or a neutrino factory and MICE– 16+/8 MV/m peak accelerating field– Peak input RF power ~ 4.6/1 MW per cavity (85% of Q0, 3τ

filling)– Average power dissipation per cavity ~ 8.4/1 kW – Average power dissipation per Be window ~ 100/12 watts




Recent progress for the welding

fmeasured = 200.88 MHz




Ready For Equator Welding




Extruding tests at JLabExtruding tests at JLab




RF Coupler

Curved Be windows




Evolution of the pre-curved window

Earlier window geometry:

Concave radius > convex radius

Intersecting point

Concave radius R = 500mm

Convex radius R=230.8mm

Current window geometry

Concave radius < convex radius

770 mm

Intersecting point

Convex radius = 498.11 mm

Concave radius= 300 mm




Curved window thickness: 0.38 mm(100 C temperature gradient)

Stress results

Max stress 177 MPa

Max stress 170 MPa

Displacement:

3-D model

Max bow 2.1 mm

2-D model

Max bow 2.25mm




Analysis on the prototype window for 805 MHz cavity

The new geometry – 16cm diameter window




Curved Be windows by BWM

Two curved Be windows for 805 MHz cavity: 0.254 mm thick and 16-cm diameterPre-formed the Be foils first at high temperature, brazed copper frames afterwards.The windows will be Ti nitrided at LBNL for high power test at MTA, Fermilab.




The 1st mode frequency in 3D model is reasonably agree with that of its 2D model’s and also good agreement with ALGOR 3D result (1696 Hz).

Solution from ANSYS

3D meshed ANSYS model The 1st mode: 1695.3 Hz

Mechanic Resonances




The 9th mode: 4560 Hz

Solution from ANSYS

The 2nd and 3rd mode: 2055 Hz The 4rd and 5th mode: 3494 The 6th mode: 3754 Hz

The 7th mode: 3768 Hz

The 8th mode: 4544 HzThe 10th mode: 4866 Hz

Higher Mechanic Resonance Modes

Controls




Discussions on Blondel’s table

∆E: A few times 10-3 of tolerance for RF voltage and phase

– Voltage stability of 10-3 is very difficult (impossible)– Phase stability: 0.5 degree – Measurement on beam

Do best to keep the voltage as stable as possible




Summary

• 8 MW peak RF power sources have been identified, need to see actions (plans) on refurbishing and conditioning various components soon

• RF distribution system: hybrids versus circulators – Should reach an agreement for MICE soon

• Cavity prototype – Equator welding tomorrow (April 1, 2004)– Ready for ordering curved 201 MHz Be windows– Ready for high power test at MTA, Fermilab this fall

• Controls

report from rf session (1:30-5:40 pm, 3/30/2004) h. haseroth and derun li center for beam physics...

Documents

rf layout

rf session derun li

rf power design

mice rf power sources

rf power amplifiers

mw peak rf power

rf driver amplifiers

rf power baseline design