status of the 201 mhz cavity and coupling coil module steve virostek lawrence berkeley national...
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Status of the 201 MHz Cavity and Coupling Coil Module
Steve Virostek
Lawrence Berkeley National Laboratory
MICE Video Conference
March 10, 2004
March 10, 2004MICE Video Conference
Status of 201 MHz Cavity and Coupling Coil S. Virostek
LBNL Page 2
201 MHz Cavity Concept
Spinning of half shells using thin Cusheets and e-beam welding to join theshells
Water coolingchannels
Cavity design accommodatesdifferent windows
Extruding ports
March 10, 2004MICE Video Conference
Status of 201 MHz Cavity and Coupling Coil S. Virostek
LBNL Page 3
The Cavity Body Profile
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 permits spinning technique and mechanical tuners similar to SCRF ones
Stiffener ring
Bolted Be window
March 10, 2004MICE Video Conference
Status of 201 MHz Cavity and Coupling Coil S. Virostek
LBNL Page 4
The Cavity Parameters
The cavity design parameters – Frequency: 201.25 MHz– β = 0.87
– Shunt impedance (VT2/P): ~ 22 M/m
– Quality factor (Q0): ~ 53,000
– Be window radius and thickness: 21-cm and 0.38-mm
Nominal parameters for cooling channel in a neutrino factory – Up to 17 MV/m peak accelerating field
– Peak input RF power ~ 4.6 MW per cavity (85% of Q0, 3τ filling)
– Average power dissipation per cavity ~ 8.4 kW– Average power dissipation per Be window ~ 100 watts
March 10, 2004MICE Video Conference
Status of 201 MHz Cavity and Coupling Coil S. Virostek
LBNL Page 5
Spinning @ ACME
Spinning a bowl
Spinning tools
An example of the spinning technique!
March 10, 2004MICE Video Conference
Status of 201 MHz Cavity and Coupling Coil S. Virostek
LBNL Page 6
RF & CMM Measurements at LBNL
CMM scans, RF frequency andQ measurements of half shells;Cu tape for better RF contacts.
201 MHz Muon Cavity Shell #1 CMM Profiles
0
4
8
12
16
20
0 10 20 30 40 50 60
Radial Dimension (cm)
Axi
al D
imen
sio
n (
cm)
3 CMM scans per half shell conducted at 0o, 45o, 90o, respectively.
Measured frequency: 196.97 MHz
(simulated frequency: 197.32 MHz)
March 10, 2004MICE Video Conference
Status of 201 MHz Cavity and Coupling Coil S. Virostek
LBNL Page 7
E-Beam Welding
Preparation for e-beam welding of thestiffener ring (left); after the e-beam Welding (above)
Stiffener ring
March 10, 2004MICE Video Conference
Status of 201 MHz Cavity and Coupling Coil S. Virostek
LBNL Page 8
Extruding Tests at JLab
Extruding tests on a flat Cu plate going through e-beam joint
Possible improvement:Anneal around the extruding area orCombination between pilot hole dimensions and lid heights, …
Successful extruding recently!
March 10, 2004MICE Video Conference
Status of 201 MHz Cavity and Coupling Coil S. Virostek
LBNL Page 9
Be Windows R&D
• Ideal windows– Transparent to muon beams– Perfect electric boundary to RF field– No detuning of cavity frequency
• Engineering solutions– Pre-stressed flat Be (low-Z) windows– Pre-curved Be windows– Grids
A pre-curved Be window:0.25 mm thick and 21 cm in radius
Window profile
evolutions
March 10, 2004MICE Video Conference
Status of 201 MHz Cavity and Coupling Coil S. Virostek
LBNL Page 10
Curved S.S. Windows
Succeeded in the S.S. window with Cu frame for 805 MHz cavity(scaled version of the window for 201 MHz cavity)
Pre-formed at room temperature by holding foil edge then brazing the Cu frames
A finished curved S.S. window with brazed Cu frame
March 10, 2004MICE Video Conference
Status of 201 MHz Cavity and Coupling Coil S. Virostek
LBNL Page 11
Curved Be Window
Failed in forming Be window at room temperature
The curved Be windows can be formed at higher temperature by the Brush-Wellman Company. Order was placed for two 805 MHz windows.
The Be foil cracked during forming at room temperature (LBNL)
A successfully formed Be foil (Feb. 5th 2004 at Brush-Wellman)
March 10, 2004MICE Video Conference
Status of 201 MHz Cavity and Coupling Coil S. Virostek
LBNL Page 12
Curved Be Windows
Brush-Wellman recently succeeded in making two curved Be windows with Cu frames for the 805 MHz cavity
Fabrication Methodology
•Fabricated dies in the shape of the windows
•Press Be into shape at high temperature
•Braze Cu frames to curved Be in a separate process
March 10, 2004MICE Video Conference
Status of 201 MHz Cavity and Coupling Coil S. Virostek
LBNL Page 13
201 MHz Cavity Status
Four half shells have been formed by spinning Cu stiffener rings were e-beam welded to two half shells The shells were mechanically cleaned at JLab Shells are being machined prior to e –beam welding of equator joint Equator weld fixturing has been fabricated at LBNL Cavity nose piece rings (fab. By U. Miss.) have been brazed at LBNL Conceptual design of RF loop coupler is complete Prototype pre-curved Be windows complete (805 MHz size) E-beam welding of equator joint and nose rings Extruding of four ports (2 RF, 2 vacuum) Brazing of cooling lines to cavity exterior Chemical cleaning and electro-polishing of the cavity Design and fabrication of tuner system Final design and fabrication of RF coupling loops The cavity should be ready for test in MTA at Fermilab this fall
March 10, 2004MICE Video Conference
Status of 201 MHz Cavity and Coupling Coil S. Virostek
LBNL Page 14
MICE RF Module Layout Status
New layout has several changes and additions:
New coupling coil design incorporated
RF coupling loops modified
Vacuum system for cavities and vessel added
AFC module vessel flanges extended 62 mm on downstream ends to make flanges symmetric to coils
Various vessel joint concepts being explored
March 10, 2004MICE Video Conference
Status of 201 MHz Cavity and Coupling Coil S. Virostek
LBNL Page 15
MICE RF Module Layout
March 10, 2004MICE Video Conference
Status of 201 MHz Cavity and Coupling Coil S. Virostek
LBNL Page 16
MICE RF Module Coupling Loops
March 10, 2004MICE Video Conference
Status of 201 MHz Cavity and Coupling Coil S. Virostek
LBNL Page 17
MICE RF Module Vacuum System