summary of the rf parallel session steve virostek lawrence berkeley national lab mice collaboration...

Summary of the RF Parallel

Session

Steve VirostekLawrence Berkeley National Lab

MICE Collaboration Meeting 18 June 16, 2007

Summary of the RF Parallel Session Talks from MICE CM18

Steve Virostek - Lawrence Berkeley National Lab

RF Session Talks

MuCool RF Program: RF Cavity R & D

(A. Bross)

RFCC Module Design Update

(S. Virostek)

Coupling Coil Integration with the RFCC Module

(S. Virostek)

MuCool RF Program:RF Cavity R & D

805 and 201 MHz Studies

ANL / FNAL / IIT / LBNLU Miss / Cockcroft

Alan Bross




MuCool Test Area



MuCool Test Area

• Facility to test all components of cooling channel (not a test of ionization cooling)– At high beam power

• Designed to accommodate full Linac Beam

• 1.6 X 1013 p/pulse @15 Hz

– 2.4 X 1014 p/s

– 600 W into 35 cm LH2 absorber @ 400 MeV

– RF power from Linac (201 and 805 MHz test stands)• Waveguides pipe power to MTA



MTA Hall



805 MHz •Data seem to follow universal curve

– Max stable gradient degrades quickly with B field

•Remeasured– Same results– Does not condition

Gra

die

nt

in M

V/m

Peak Magnetic Field in T at the Window



805 MHz Imaging



805 MHz Sparking Damage Curved Be Window after

Processing in Magnet Field

Small amount of sparking damage on upstream window at 12 o’clock (least damage seen in Studies). Cavity bright & clean. Damage on copper iris is mainly from previous testing.



Next 805 MHz study - Buttons

Button test– Evaluate various materials and coatings– Quick change over

Field Profile



First Set of Button Data – TiN Coated Cu



TiN Coated Cu – After Running



RF R&D – 201 MHz Cavity Design•The 201 MHz Cavity is now operating

– New x-ray background data collected (see Alan’s talk)



201 MHz Cavity Status

•The flat Cu windows have been replaced w/curved Be windows

•Slower conditioning and more sparking than with the Cu. May be due to better clean room at J-Lab during initial installation.– However, MTA CR air quality was measured at class 100 or better

•So far the 201 w/Be windows has been conditioned to ~5MV/m

•No running for >3 weeks due to 201 power source problems – Note: The cavity is now out of tune (beyond the range of power source)

and must be re-tuned via the jacking screws

– Cavity frequency dropped ~400 kHz w/curved Be windows installed

– Will get help @Fermilab from LBNL to do the tuning



Clean Room for 201MHz Cavity



201 MHz Sparking Damage on Flat Copper Window

coated with TiN over center portion

The inside of the cavity appeared bright & clean

•Very little spark damage after RF processing to 18 MV/m

•One copper splatter visible (photo)



Curved Be window Installation

Tyvek-wrapped Mike Dickinson and Ben Ogert installing one of the Be windows



Plans for the MTA

•Continue 805 MHz button tests w/bare & TiN coated buttons

•We have buttons made with the following metals– Tantalum – Tungsten – Molybdenum-zirconium alloy– Niobium– Niobium-titanium alloy– Stainless steel

•Continue conditioning 201 with Be windows (if power ever becomes available) without B field (after re-tuning).

– Then do B field scan • Can go up to few hundred gauss at present• Need new pumping system to go higher • And eventually Coupling Coil



Coupling Coil Layout in the MTA

RFCC Module Design

Update automatic tuners

cavity suspension

cavity installation





RF Cavity & Coupling Coil Modules in MICE

RFCC Modules



Updated RFCC Module 3D CAD Model

201 MHz RF cavity

Automatic tuners

Cavity suspension



Cavity Tuner Design Features•Six evenly spaced automatic tuners per cavity provide frequency adjustment

•Layout avoids interference with cavity ports

•Tuners touch cavity and apply loads only at the stiffener rings

•Tuners operate in “push” mode only (i.e. squeezing)



Four Cavity Layout in Vacuum Vessel •Tuner layout

rotated 30º @ cavity pairs

•Actuators are off cavity center plane to avoid coupling coil

•Bellows connections at vacuum vessel feedthroughs

•0 to -460 kHz tuning range (0 to -4 mm)

•1.6 MPa max. actuator pressure (50 mm)



Cavity Tuner Section View

Ball contact only

Dual bellowsfeedthrough

Tuner actuator(likely air)

Pivot point

Fixed (bolted)connection



Tuner component Details

Fixed arm

Pivoting arm

Actuator& bellowsassembly

Forces are transmitted to the stiffener ring by means of “push/pull” loads applied to the tuner lever arms by the actuator assembly



•Six strut system provides kinematic cavity support

•Orthogonal strut layout is stiff and allows accurate cavity positioning

•Kinematic mounts fix cavity without over-constraint

Cavity Suspension System



Cavity Suspension System

1 vertical strut

2 horizontal struts

3 axial struts



Strut End Connection Details

One end of the struts is attached to a fixed lug welded to the ID of the vacuum vessel

The cavity end of the vertical and one of the horizontal struts are attached directly to the stiffener ringThe cavity end of the axial and one of the horizontal struts are attached to the fixed leg of a tuner



Four Cavity Layout in Vacuum Vessel •Dedicated struts

(6) for each cavity

•No contact between cavity pairs

•Struts axially fix the outside walls of the cavity pairs

•Tuning deflections increase cavity gap



Cavity Installation Sequence

•Pre-assemble cavities with Be windows and tuners (w/o actuators)

•Slide inner cavities into vacuum vessel using spacer/alignment blocks

•Shim cavity to align tuner & coupler vacuum feedthrus with tuner mounts and cavity ports

•Install struts, tuner actuators and RF couplers

•Repeat same process for outer cavities

Coupling Coil

Integration with the

RFCC Module





Coupling Coil Integration Topics

•New coupling coil design developed by LBNL & ICST (Harbin)

•Increased coil length (+35 mm to 285 mm) results in longer vacuum vessel

•Integration issues w/tuners and RF, vacuum & diagnostic cavity ports

•Must transmit magnetic forces from the cold mass supports to the vacuum vessel

•New 3D model developed by LBNL for integration



Reinforcing plates

Indented sections

Servicetower

Cryocoolers

Support cone

Cold mass supports

Coil assembly

He cooling pipes

Coupling Coil Design Configuration

Coupling Coil Gusset Connections

Gussets between cold mass support cones and vacuum shell transmit magnetic forces

Tuner actuators nest between gussets



Upper Cold Mass Support Cones

Weld

Weld



Connection to Support Side Plate

Support stand side plate

Weld

Tuner cutout

Interior gusset



Vacuum Vessel Assembly to Coil

Vacuum weld on interior



RF Coupler/Coil Interface

Coupler vacuum sleeve nests in coil vacuum shell recess (3 mm gap)



Vacuum System/Coil Interface

Vacuum manifold

Vacuum pump

Gate valve



Vacuum System Integration

Inside cavity vacuum connectionOutside cavity vacuum connection

Vacuummanifold

Vacuum pump

Gate valve



Vacuum Manifold/Coil Interface

Vacuum manifold end nests in coil vacuum shell recess (3 mm gap)

summary of the rf parallel session steve virostek lawrence berkeley national lab mice collaboration...

Documents

rf processing

rf cavity r d805

cavity designthe

cavity bright clean

virostekmucool rf program

sparking damage curved

flat copper window

mevrf power