Antiproton Acceptance

1
Antiproton Acceptance

• Keith Gollwitzer
• Dept. of Energy Review
• March 30, 2005

2
Outline

• Goal
• An admittance of AP2 and Debuncher in each plane
  to be 35 ? mm-mrad
• Accepting 320 ? mm-mrad beam emittance
• Transfer efficiently to Accumulator via D/A
• Mitigation
• Orbit Control
• Instrumentation
• Other Work
• Beam Studies
• Character of studies has changed from
  predominately dedicated reverse proton studies to
  mostly semi-parasitic stacking studies
• Aperture Finding

3
What Where - Mitigation
Extraction Kicker (SD2005)
Beam Stop (SD2004)
Move DRF2 (SD2004) and DRF3 (SD2003)
Injection Region (SD2004)
Shutdown
Open Debuncher Only Filled AP2Debuncher
Vertical Band 4 - Widen Array Gap (SD2005)
Italic underlined items discussed later
4
Mitigation of Limiting Apertures Debuncher
Injection Area

• Debuncher Injection Area Modifications
• Injection septum common vacuum
• Replace D4Q4 SQC quadrupole with two LQB
  quadrupoles
• Motorize injection septum and kicker stands
• Vacuum system modifications
• Bigger D4Q4 vacuum chamber
• Move BPM to downstream of D4Q4

5
Mitigation of Limiting Apertures Debuncher
Injection Area

• Old Layout

6
Mitigation of Limiting Apertures Debuncher
Injection Area
Added AP2 BPM just upstream of D4Q5
7
Mitigation of Limiting Apertures Debuncher
Injection Area
D4Q4a

• New Layout

D4Q4b
Septum
8
Mitigation of Limiting Apertures Debuncher
Injection Area

• Injection Septum Common Vacuum

9
Mitigation of Limiting Apertures Debuncher
Injection Area

• D4Q4 Aperture

New
Old
Note Injected and circulating beam are
vertically separated.
10
Mitigation of Limiting Apertures AP2 Beam Stop

• AP2 Beam Stop and Vacuum situation prior to 2004
  Shutdown. Small vacuum leak at window next to
  Beam Dump. Installed pair of windows between Q2
  and Q3. Eventually, upstream end let up to air
  (red section). Pair of vacuum windows at large ?
  function multiple scattering.

Removed Q1 and Q2 to remove Beam Stop and
cantilevered beam tube from Steel Shielding. Took
opportunity to survey alignment of AP2 wrt to
pulsed magnet and map out the shielding
passage. Determined that Shielding forced
non-optimal alignment of Beam Pipe and Beam Stop
see slide. Moved Beam Stop downstream (pass
Q6) and installed a shorten beam pipe
cantilevered from Q1 see slide. Reduces
multiple scattering with removal of windows and
reducing path in air.
11
Mitigation of Limiting Apertures AP2 Beam Stop

• Mis-alignment of AP2 beam stop beam pipe

mm
m
12
Mitigation of Limiting Apertures AP2 Beam Stop

• Horizontal aperture after removal of AP2 beam
  stop

mm
m
13
Mitigation of Limiting Apertures AP2 Beam Stop

• Secondaries yield to downstream end of AP2 line
  increased 10 as a consequence of the removal of
  the AP2 beam stop.
• Plans
• Plan to install new beam stop downstream of Q704
  during the Fall 2005 shutdown.

14
Yet to be Corrected Limiting Apertures

• Widen Vertical band 4 cooling arrays for pickup
  and kicker
• Upgrade arrays during 2005 shutdown
• Likely requires 8 week shutdown
• Debuncher extraction kicker Ceramic Pipe
  module modifications
• The upgrade will be installed during the 2005
  shutdown.
• Will also motorize extraction kicker stand

Injected Beam Profile
Current ceramic pipe
Downstream End
Upstream End
15
Limiting Apertures
Not to be changed
The numbers in this column were calculated
using b-functions at Dp/p 0
Central orbit (?p/p 0) limiting apertures
Current Measurement Horizontal
36.0 ? mm-mrad 29.5 ? mm-mrad
Vertical 29.9 ? mm-mrad 24.9 ?
mm-mrad Combined effect of Band 4 Vertical and
Extr. Kicker upgrades is 7.4
(from particle tracking).
16
What Where Orbit Control
DEX Bump Dipoles (SD2004)
2 Trim Dipoles (2002)
2 Trim Dipoles (2003)
Shunts (2001)
Shutdown
Motorized Stands 5 Quads (SD2000) 10 Quads
(SD2003) 20 Quads (SD2004)
Open Debuncher Only Filled AP2Debuncher
Now capable of bumping locally throughout the
Debuncher (all 3-bumps have been verified). Can
add additional AP2 trims as needed.
Italic underlined items discussed later
17
Orbit Control Debuncher EXtraction Bump

• During reverse proton studies during 2004, we
  achieved an admittance of greater than 35 ?
  mm-mrad horizontally!
• This was achieved with a closed orbit bump
  through the extraction region horizontal
  position bump at the Debuncher extraction septum.
• However, not able to transfer efficiently to the
  Accumulator via D/A beam line bumped to far away
  from septum for extraction kicker.
• This has led to adding a ramped Debuncher
  EXtraction (DEX) bump.

18
Orbit Control Debuncher EXtraction Bump

• Large Injected Beam
• Beam Cooled during cycle
• Rapidly ramp DEX bump at end of cycle to put beam
  next to septum

Time in cycle
Extraction Channel of Septum
19
Orbit Control Debuncher EXtraction Bump

• Status
• Two trim dipoles installed in Debuncher during
  the Fall 2004 shutdown
• All cables to the tunnel have been pulled
• Power supplies built by EE support
• Commissioning beam studies (March 2005)
• Ramps built and locality verified
• Implentation

20
What Where - Instrumentation
Debuncher pbar TBT (2004)
Upgrade BPM system (Spring 2005)
Toroids (Spring 2005)
Debuncher Pbar Intensity Monitor (2005)
Shutdown
D/A Upgrade BPM system (Spring 2005)
D/A Toroid (Spring 2005)
Open Debuncher Only Filled AP2Debuncher
Upgraded BPM system Closed Orbit at 2.5MHz (2004)
Upgraded BPM system Closed Orbit at 53MHz (Summer
2005)
Accumulator pbar TBT (2005)
Italic items discussed later
21
Instrumentation Recent and Ongoing

• Debuncher pbar Intensity Monitor see slide
• Ongoing modification of Debuncher BPMs for Closed
  Orbit readout during stacking
• AP2 and D/A BPMs see slide
• Deb. Extraction kicker noise issues resolved
• DAQ hardware software upgrade in progress
• Debuncher pbar Turn-By-Turn has been made more
  robust
• Accumulator pbar Turn-By-Turn has been built and
  implemented see slide
• Debuncher loss monitor system checked out and
  calibrated during shutdown

22
Instrumentation Debuncher Pbar Intensity Monitor

• Requires ramping DRF1 in the middle of the
  stacking cycle and then ramp back down
• Block diagram of temporary intensity monitor
• Working on modification to get pbar closed orbit
  while stacking

23
Instrumentation AP2 BPM Prototype Response

• Timelines have several types of slip-stacking
  events (normal, switchyard NUMI) which cause
  different AP2 orbits.
• One can see the different timelines and the
  number of each type of different slip-stacking
  events.
• Intensities in the Debuncher change with the
  different slip-stacking events (not shown).
• A target tune of an AP1 trim dipole was done and
  the BPMs track.
• BPM sum signals follow the established intensity
  measurement in AP2.

24
Instrumentation Accumulator Turn-By-Turn
Requires bunched beam at end of Debuncher
stacking cycle. There is no attempt to
phase/frequency match with ARF1. (ARF1 is the RF
system which is used for moving beam from
Accumulator injection to stacktail deposition
orbit.) Hence, stacking efficiency takes a hit
while closing the D2A line into the Accumulator.
Shown is a scan of the Debuncher Extraction
Septum and the TBT response for several settings
(right plot). The oscillations from a single
injection is also shown. Scales are arbitrary.
25
Other Work

• Lattice Development
• Debuncher Lattice measurements have been
  incorporated into model.
• Updates and addition of more complete physical
  aperture dimensions and locations
• Survey
• Completion of optical/laser survey of AP1, AP2,
  Debuncher D/A line performed during 2004
  shutdown
• Confirmed offset of V730 of AP2 and reset dipole
• D/A analysis completed and led to septa moves
• Cross checks of remaining data sets are being
  done
• AP2 Chromatic Studies
• Simulation studies of transport of beam from
  target to circulating in Debuncher (LBNL)

26
Beam Time

• Most of 2004 reverse protons
• Commissioning of Debuncher BPMs, motorized quad
  stands and local bumps, Running Wave for
  identifying aperture limitations see slides
• Small gains made over several months
• Large gain Horizontally with bump at extraction
  septum
• However, kicker unable to compensate (essentially
  no gain to stack rate)
• Has led to ramped Debuncher Extraction (DEX) bump
  earlier slides
• Some work done with procedures and diagnostic
  tests for reverse protons up AP2.
• Since shutdown some reverse protons
• Commissioning of motorized quad stands and local
  bumps (including DEX)
• Recovery of admittance after shutdown
• Further tests of beam up AP2
• Since shutdown mostly semi-parasitic stacking
  studies
• Commissioning of instrumentation to see 108
  pbars associated procedures
• Component Centering see slides
• Bumping around the Debuncher see slides

27
Aperture Finding Reverse Protons

• Running Wave
• Two trim dipoles playing sin and cos curves to
  test for aperture limitations
• Beam is heated in appropriate plane
• One period of curve is run to prep beam
• Inherent diffusion repopulates the beam edge
  which is then scraped away by limiting
  aperture(s) in successive periods of Running Wave
  curve
• Relies upon monitoring beam current and loss
  monitors for each step of Running Wave curve
• Made available fast updating beam current signal
• Loss monitors received full checkout and
  calibration during 2004 shutdown

28
Aperture Finding Reverse Protons
Beam Size (arb)
Phase Advance (arb)
Apertures Phase wrt to Running Wave
Beam Current (arb)
Running Wave Cartoon
Phase Advance (arb)
29
Identification of limiting Apertures Reverse
Protons

• Aperture Finding Running Wave

30
Aperture Finding - Stacking

• Semi-parasitic stacking studies
• Component Centering about beam
• Local Bumping Around Debuncher
• Centering and Bumping require
• Ability to determine pbar intensity in the
  Debuncher earlier slide
• Stability of upstream machines and/or offline
  analysis to disentangle different slip-stacking
  cycle effects
• Patience to perform a bump since motorized quad
  stands controls only allow moving a single stand
  at a time
• First component is changed make a 1-bump
• Second component is changed now have 2-bump
• Third component is changed closes to make a
  local 3-bump
• Can take several minutes to complete the bump
• Depending upon the number of motorized quad
  stands in a bump, a scan can take 10 to 30
  minutes to perform

31
Identification of limiting Apertures Stacking

• Bumping around the Debuncher
• Center moveable devices on beam.
• Built high precision Debuncher intensity monitor
  (DBPI10D).
• Construct 3-bumps that cover the Debuncher (43
  horiz. 42 vert. bumps)
• During stacking, move each bump ?2 mm while
  monitoring Debuncher intensity.

Measured during Stacking
32
Summary

• Much work has been done in making tools and
  procedures for Beam Based Alignment
• Will continue-
• Rounds of local bumping in Debuncher
• Component centering about orbit after each round
  of bumping
• Completing DEX bump commissioning
• Commissioning AP2 and D2A BPM system
• Maximize Debuncher injection aperture via reverse
  proton studies
• Measure AP2 lattice
• Center orbit in AP2 using both reverse protons
  and stacking secondaries