Commissioning of the Fermilab
Accelerators for NuMI Operation
Robert Zwaska
University of Texas at Austin
NBI 2003
November 7, 2003

Fermilab as a Proton Source•

Protons accelerated to 8 GeV in Booster¾ 474 m Circumference¾ 5 x 1012 protons / batch (maybe 6 x1012)¾ 15 Hz repetition rate

Main Injector accelerates
to 120 GeV• As many as 6 batches• 1 must go forantiproton production¾ Cycle time > 1.9 s• Depends on antiprotonsource needs

INOS¾ 3320 m Circumference(7x Booster)¾ Multiple batches ofBooster beam injectedNuMI/M•

Protons for NuMI
• Proton Math: protons•

seconds
Booster Batches
seconds
protons×5
÷τ
× 1.9E7year
MI Cycle
MI Cycleyear
Booster Batch
MINOS initial request: 8 x 1020 protons=¾ 4 x 1013 / pulse ⇒ 2.5 x 1013 / pulse¾ 4 x 1020 / year ⇒ 2.5 x 1020 / year
¾ Request has not decreased• MINOS 5 year plan
• http://hep.caltech.edu/~michael/numipiwg/fiveyear/fiveyear.ps¾ Calls for increasing proton rate → 7.5 x 1020 / year
¾ Various small improvements• c.f. Finley Report:
http://www.fnal.gov/directorate/program_planning/studies/ProtonReport.pdf• Prospects of a proton driver¾ Potentially increase to 20 x 1020 / year
• http://www.fnal.gov/directorate/Longrange/ProtonDriver_Open_Meeting.html
November 7, 2003

Robert Zwaska
NBI 2003

3

Challenges to NuMI
• Must coexist with collider
program• Main Injector issues¾ Multibatch commissioning¾ 8 GeV lifetime¾ Dampers¾ Beam Permit¾ RF Power¾ Involves accelerating twobeams in MI, simultaneously¾ Timing issues are shared• PBar cooling time

• Requires high performance ofaccelerators• Booster Issues¾ Well in excess of previous
levels of operation¾ Intensity¾ Losses & radiation¾ Multibatch timing• Beam quality requirements¾ Cannot afford high losses inNuMI primary line

November 7, 2003

Robert Zwaska
NBI 2003

4

Main Injector Commissioning••

Main Injector has not operated inmultibatch mode•

¾ Not necessary yet•

Two beams must be accelerated together¾ Extracted to PBar & NuMI

NuMI will require continuous multibatch
operation¾ Simultaneous with antiproton production

Total intensity is more than six time thecurrent running¾ 2.5 x 1013 for NuMI
¾ .8-1.0 x 1013 for PBar
¾ Currently only do ~ 0.5 x 1013

Booster
Batch 1 (pbar)½ Batch(empty)½ Batch(empty)Batch 2Batch 6Main Injector

Batch 3Batch 5
Batch 4

Starting multi-batch operation in MI
A. Marchionni, B. Choudhary, H. Kang,
S. Mishra, R. Zwaska• 6 batches, increasing
Booster turnsMay ‘03• 6 batches, 14 Boosterturns

Limit of~ 2.5 x 1013November 7, 2003

Robert Zwaska
NBI 2003

6Damping Oscillations• Individual buckets of the beam
oscillate about the ideal orbit• Has many causes:¾ Injection errors¾ Intrabeam interactions¾ Magnetic field inhomogeneities• Oscillations grow with time
unless unchecked• Previously, damper systems
have only been able to damp
specific modes of oscillation• Digital technology allows a
new method
November 7, 2003

Robert Zwaska
NBI 2003

7

Digital Bunch-by-Bunch Dampers
B. Foster, H. Kang,••

Damp the oscillations of eachbunch independently of the rest
¾ More natural way to do it

Damper kick is calculated fromsingle BPM position reading on 3
successive turns

Requires very fast pickups,kickers, and electronics¾ Arbitrary Betatron Phase ofKicker can be accommodated¾ Bunches are spaced 19 ns apart¾ Beam revolves in 11 µs••

Individual oscillations are damped
in a few msBPM

KICKER

Horizontal
damper pickup

Longitudinalkickers

Multibatch with Dampers• Beam can survive injection¾ 3.3 x 1013 captured andaccelerated to ~ 25 GeV¾ Enough for “baseline”
operation

3.3×1013• Still cannot accelerate
through transition because ofRF
¾ Primarily a matter of settings¾ Will be fixed soon

November 7, 2003

Robert Zwaska
NBI 2003

10

Main Injector Beam Permit for NuMI
S. Mishra, K. Wu• This is required during operation and commissioningof the NuMI beamline,¾ Avoid beam losses in the NuMI beamline due to poor
quality beam extracted from MI• Needs a set of appropriate fast signals from Main
Injector¾ Indicative of beam quality, need to be identified• Signal provided to the NuMI permit system¾ Used to abort beam extraction to the NuMI beamline whenthe quality criteria are not met• Beginning to write specifications for the system
November 7, 2003

Robert Zwaska
NBI 2003

11

“Proton Economics”
8 GeV Proton Demand•¾ Only accelerates one
Booster batch now¾ Needs to do six

Protons/Hour (1E16)•

Booster is the oldest ringat Fermilab
Throughput has toincrease several times
Main Injector needs tofinish its commissioning

20
18
16
14
12
10
86
420

MiniBooNEBegins

NOW

NUMI/MINOS

PresentOperatingLevel

Shortfall

pbar max w/slipstacking

Q
3Q 200
4 1Q 200
1 1Q 200
2 2Q 200
3 2Q 200
4 2Q 200
1 2Q 200
2 3Q 200
3 3Q 200
4 3Q 200
1 3Q 200
2 4Q 200
3 4Q 200
4 4Q 200
1 4Q 200
2 5Q 200
3 5Q 200
4 52005•

Fancy MILoading schemes(or >5E12)

Calendar Quarter

November 7, 2003

Robert Zwaska
NBI 2003

12

Booster as the Bottleneck• Originally accelerated < 2 x 1012 once every few
seconds• Now needs to accelerate > 5 x 1012 at 5 – 8 Hz
• Pulsed devices became a major concern¾ Many have been upgraded/replaced• Beam physics has to be understood on a new level¾ Space charge & instabilities¾ Details of magnet lattice• Radiation becomes amore significant problems¾ Prompt radiation outside the tunnel increases¾ Radioactivation inside the tunnel also increases¾ Booster rate is limited by radiation from losses

November 7, 2003

Robert Zwaska
NBI 2003

13

Booster Dogleg•

Set of four DC dipole magnets know as a double“dogleg”

SeptumMagnet¾ Also known as chicane••Bends the beam around extraction septum
magnet
The dogleg magnets have edge focusing effects
and higher order fields

Extracted Beam

¾ Disturbs the lattice throughout the cycle,
particularly during injection¾ Increases β by 50%¾ Increases Dispersion by 100%

•Fixed by increasing separation ⇔ reducing
magnet strength

November 7, 2003

Robert Zwaska
NBI 2003

Dogleg Magnets

14

Radiation Issues• Radiation is the driving limit on
Booster operation• Residual activation in the tunnel¾ Radioisotopes created by showers¾ Long lived isotopes limit how much
maintenance can be done in thetunnel• Damage of beam components• Prompt radiation from theshowering of lost protons¾ Radiation scales with energy andnumber of protons lost
¾ Very small amount penetrates theshielding
November 7, 2003

Robert Zwaska
NBI 2003

15

Collimators• Intentionally limit theaperture in a location• Collect the resulting losses
into three big blocks of steel

November 7, 2003

• Do not reduce losses in total• Do reduce losses in criticalareas• Expected (hoped) to reduce
uncontrolled losses by ~ 90%

Robert Zwaska
NBI 2003

16RF Prototype Project•

Booster RF cavities¾¾¾¾•

18 in total around ring
Currently are the limiting aperture (2.3”)
Most losses occur in the RF cavities
Unfortunately most maintenance required isin the RF cavities!

Plan: replace RF cavities with 5” aperture
design from proton driver study•

Pilot program to replace two RF cavities. Universities
involved:¾ MINOS: UT-Austin, Caltech, Tufts¾ MiniBoone: Indiana, Nevis, Princeton•••

November 7, 2003

All parts machined, delivered in April/May, ready forassembly this summer
Substantial savings to FNAL over in-house fabrication
Intention to install this Fall ’03 shutdown, probably
postponed til January.

Robert Zwaska
NBI 2003

17

Need for a Notch•

Extraction kicker has a risetime of ~ 40ns

6.5e12¾ Only ~ 10 ns between bunches•LossesBeam lost at 8 GeV¾ Losses on septum magnet¾ Already significant there•

Nominal Notch

Intensity

8 GeV losses would limit the PBar
program¾ MiniBooNE & NuMI would be almost
inoperable•

Instead, remove the beam at 400 MeV¾ Can choose where to lose it¾ Called a “notch” in the beam•

3 ms Delay

Beam currently notched with a fastkicker

4 ms Delay¾ Will be resonantly pinged into thecollimators

4.5e12

November 7, 2003

Robert Zwaska
NBI 2003

18

Booster – MI Timing → Cogging

Main Injector

R. Zwaska, B. Pellico

84 RF buckets
around circumference
Previous injected
Booster batch

••
•
•
•

Booster

Notch

Booster beam has the notch in it
Requires extraction to MI to be synchronized with the notch
Extraction must also be synchronized to the beam already in theMain Injector
Problem: The Booster and Main Injector are not synchronized“Cogging”: forced synchronization of beams¾ No Booster flattop to fix at the end¾ Active feedback during acceleration necessary

November 7, 2003

Robert Zwaska
NBI 2003

19

Cogging Beam Studies• Predict relative slippage¾ Measure in first ~ 3 ms
¾ Place notch intelligently• Radial Feedback late in the cycle¾ Changes energy & circumference¾ Induces slippage

Notch

2.4e12+6 mm

Intensity

RadialFeedback

RadialFeedback

November 7, 2003

0e12-6 mm 0 ms

Robert Zwaska
NBI 200333 ms20

Summary• NuMI is an entirely new mode of operation for Fermilab¾ Must run simultaneous with the Collider• NuMI requires Main Injector to be commissioned for multibatchoperation¾ MI designed for this, but never shaken out¾ Program underway to commission before NuMI turn-on• Booster can potentially limit the program¾ Limited in per pulse intensity• Marginal improvements underway¾ Limited by radiation• Major improvements underway• Also important for MiniBooNE¾ Must be commissioned for multibatch operation → Cogging

November 7, 2003

Robert Zwaska
NBI 2003

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