1. E-beam scanner experience at FNAL
9th DITANET Topical Workshop on Non-Invasive Beam Size Measurement for High Brightness Proton and Heavy Ion Accelerators
15-18 April 2013
Randy Thurman-Keup… Déjà vu?
Fermilab

2. 9th DITANET Topical Workshop -- R. Thurman-Keup
State of the Lab
Fermilab currently involved in a mostly labwide shutdown
Tevatron and associated antiproton facilities turned off 1.5 years ago
Main Injector and Recycler are being modified to support combined operation where
Recycler accumulates protons from the Booster
Protons are transferred to the Main Injector
Recycler accumulates more protons while simultaneously the Main Injector ramps the energy from 8 to 120 GeV and sends them to the Nova neutrino experiment in Minnesota
This parallel running will reduce the cycle time by a factor of two
Main Injector parameters
588 buckets; 500 filled; 1 abort gap
1-2 ns longitudinal sigma
3 mm horizontal x 1 mm vertical sigma (at the proposed location of e beam scanner)
1 x 1011 particles per bunch
16 April 2013
9th DITANET Topical Workshop R. Thurman-Keup

3. 9th DITANET Topical Workshop -- R. Thurman-Keup
Main Injector
Increasing beam power in MI/RR implies the need for non-invasive instrumentation
Electron beam deflection technique is one choice (working implementation at SNS, see W. Blokland’s talk)
Electron beam is deflected by electric and magnetic fields of the protons
Deflection
Angle
Electron beam
Proton beam out of page
Deflection vs. Angle provides information about the proton beam transverse profile
16 April 2013
9th DITANET Topical Workshop R. Thurman-Keup

4. Techniques for Main Injector
Various techniques for measuring deflection
Fast scan through peak of bunch (see W. Blokland’s SNS talk)
Requires fast deflector (< 1 ns sweep time)
Slow scan, akin to flying wires (most likely solution in short time frame of Nova)
Position the beam and record the maximum deflection as the beam passes by
Leave the electron beam stationary
Sweep the beam along the proton direction
Obtain longitudinal distribution
Collaborating with Wim Blokland at SNS who is doing simulations of the various techniques
16 April 2013
9th DITANET Topical Workshop R. Thurman-Keup

5. 9th DITANET Topical Workshop -- R. Thurman-Keup
Electron Deflection
Slow electron sweep
Position the electron beam
Record the deflection of a bunch
Move the electron beam and repeat
Plots courtesy of Wim Blokland
16 April 2013
9th DITANET Topical Workshop R. Thurman-Keup

6. Electron Deflection Simulation
Step the electron beam through the proton beam and record maximum deflections
Derivative of deflection vs. position is nominally beam profile
Derivative
Plots courtesy of Wim Blokland
16 April 2013
9th DITANET Topical Workshop R. Thurman-Keup

7. Alternative Deflection Scheme
Electron Sweep
Sweep the electron beam along the proton bunch
Sweep duration coincides with the duration of the proton bunch
Beam Sim. Transverse s = 3 mm
Meas. Sim. Transverse s = 3.5 mm
Beam Sim. Longitudinal s = 2 ns
Meas. Sim. Longitudinal s = 2.3 ns
16 April 2013
9th DITANET Topical Workshop R. Thurman-Keup

8. Simulated Camera Image
Camera frames are ~30 ms
Main Injector cycle is ~1 s
Need to step many times per frame to accumulate data fast enough for measurement
Complicated to extract each step
16 April 2013
9th DITANET Topical Workshop R. Thurman-Keup

9. 9th DITANET Topical Workshop -- R. Thurman-Keup
Electron Beam Device
Ion Gauge
Optical Breadboard
~ 60 cm x 150 cm
Ion Pump
60 KeV Electron Gun
Kimball Physics
Beam Valve
Electrostatic Deflector
Elliptical Main Injector
beampipe
Ion Gauge
Pneumatic
Insertion Device
with OTR Stainless
Steel Mirror
Optic components box
Phosphor Screen
P47, 400 nm, 60 ns decay(?)
16 April 2013
9th DITANET Topical Workshop R. Thurman-Keup

10. 9th DITANET Topical Workshop -- R. Thurman-Keup
Optics
Two optical paths: OTR screen and Phosphor screen with some shared elements
SS Mirror
Phosphor screen
45 Degree Mirror
45 Degree Mirror
Lens on moving
stage
Lens on moving stage
Filters and polarizers
45 Degree Mirror on moving stage
Image Intensifier
(Hamamatsu)
CID Camera
Megarad version
Camera Objective
16 April 2013
9th DITANET Topical Workshop R. Thurman-Keup

11. 9th DITANET Topical Workshop -- R. Thurman-Keup
Devices
Kimball Physics up to 60 KeV
(we will use up to 15 KeV)
6 mA, pulsed, 1 ms to DC
LaB6 cathode, 100 mm spot size
15 cm long ‘circular’ plates
~2.5 cm diameter
Electrostatic Deflector
Thermionic Electron Gun
Plates
Solenoid and steering magnets
Cathode
16 April 2013
9th DITANET Topical Workshop R. Thurman-Keup

12. 9th DITANET Topical Workshop -- R. Thurman-Keup
Test Stand
Optical Transition Radiation Screens
Electron Gun
Faraday Cup
Lens / Digital Camera Imaging Systems
16 April 2013
9th DITANET Topical Workshop R. Thurman-Keup

13. 9th DITANET Topical Workshop -- R. Thurman-Keup
Gun Tests
Gun has internal solenoid
Scanned beam through waist at first screen
Scanned beam sizes from Ce:YAG screens (1 A beam)
Scanned beam sizes from OTR screens (1 mA beam)
16 April 2013
9th DITANET Topical Workshop R. Thurman-Keup

14. Optical Transition Radiation
Electron energy low
Broad angular distribution
Mirror should be 15 instead of 45
Light yield over the 2 ms electron pulse
(E. Bravin, private communication)
Initial beam images determined to be blackbody
No polarization
Intensity increased nonlinearly with duration
Damage to stainless steel mirror observed
16 April 2013
9th DITANET Topical Workshop R. Thurman-Keup

15. 9th DITANET Topical Workshop -- R. Thurman-Keup
Wire Tests
Wire to simulate proton beam
e Beam pulsed on for 40 ms
Wire pulsed for 20 ms
Half the time the beam is deflected 0V
50V
100V
150V
200V
250V
300V
16 April 2013
9th DITANET Topical Workshop R. Thurman-Keup

16. Test of Electrostatic Deflector
~120 V
Deflecting Voltage vs. Deflector Length
Deflector Pulse
80 ns
500 V
Deflector Pulse
15 cm long plates
~190 V
16 April 2013
9th DITANET Topical Workshop R. Thurman-Keup

17. Electrostatic Deflector Test
Longer sweep
Bright part off screen
Beam size not uniform
Possibly due to poor pulse quality
Short sweep
Effect is similar proton bunch passing by
16 April 2013
9th DITANET Topical Workshop R. Thurman-Keup

18. Magnetic Fields in Tunnel
Need to shield beamline
First attempt will be mu metal
Electron beam
Quad busses
3500 A
5 gauss Bx
0 g By
Dipole busses
9000 A
16 April 2013
9th DITANET Topical Workshop R. Thurman-Keup

19. Electron Beam Profiler
16 April 2013
9th DITANET Topical Workshop R. Thurman-Keup

20. 9th DITANET Topical Workshop -- R. Thurman-Keup
Optics
Phosphor screen
Image Intensifier
16 April 2013
9th DITANET Topical Workshop R. Thurman-Keup

21. 9th DITANET Topical Workshop -- R. Thurman-Keup
Conclusions
Plan to install in Main Injector this shutdown
But…
Fermilab shutdown is
Running out of time
Running out of people
Electron Beam Profiler is
Behind schedule
Not an officially supported project, i.e. no priority
16 April 2013
9th DITANET Topical Workshop R. Thurman-Keup