Introduction, requirements of the LHC and LHC injectors

1
OPERATION OF THE LHC BEAMS IN THE SPS
E. Métral

• Introduction, requirements of the LHC and LHC
  injectors challenges
• The LHC zoo ? Many (proton) beams required LHC
  commissioning
• Main SPS supercycle foreseen in 2008 user names
• Some procedures references for the nominal beam
• Some words about the ion beams ( early ion beam
  produced in the SPS in 2007)

2

• Many thanks to many colleagues from OP, ABP, RF,
  BI for their explanations help during the
  2007 run preparation of this course!
• See also procedures references (from 2007) done
  by Magali http//sps-documentation.web.cern.ch/SP
  S-documentation/
• Please do not hesitate for any comment!

3
INTRODUCTION (1/13)

• 2 main challenges involved in the design of the
  LHC
• Very high magnetic field to reach the collision
  energies in the TeV range
• Very high luminosity necessary to provide
  significant event rates at this energy

Beam current
Brightness transverse bunch density
It is limited by - Space-charge effects in the
injectors... - Head-on beam-beam interaction
at collision
It is limited by - Collective instabilities -
Cryogenic load (synchrotron radiation and
wall current) - S.C. magnet quench
4
INTRODUCTION (2/13)

• ? LHC injectors challenges
• Preservation of the transverse emittance
  (brightness)
• Generation of the longitudinal structure (25 ns
  bunch spacing)

5
INTRODUCTION (3/13)
SPS operates above transition ( 21 GeV) for
LHC-type beams
Duoplasmatron Source ? 90 keV (kinetic
energy) LINAC2 Linear accelerator ? 50
MeV PSBooster Proton Synchrotron Booster ? 1.4
GeV PS Proton Synchrotron ? 25 GeV SPS Super
Proton Synchrotron ? 450 GeV LHC Large Hadron
Collider ? 7 TeV
LHC (proton) beam in the injector chain
6
INTRODUCTION (4/13) ? TRANSVERSE EMITTANCE
PRESERVATION

• The initial transverse emittance is given by the
  duoplasmatron source
• The beam is then adiabatically bunched and
  accelerated in a Radio Frequency Quadrupole
  (RFQ2) under high space charge conditions
• Fine-tuning of the 50 MeV Drift Tube Linac (DTL)
  and of the transfer line to the PSB

Normalised, at 1?
Depends on extraction aperture, electrode shape
and space charge
?
?
?
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INTRODUCTION (5/13) ? TRANSVERSE EMITTANCE
PRESERVATION

• The beams in the Linac2 are quasi square pulses
  with a length which varies depending on the user
  (the beam length varies between 25 µs and 120 µs
  and it is limited at the source)
• The nominal LHC requirement is a beam of 180 mA
  in 30 ?s at the entrance of the PSBooster
• The transverse normalised rms beam emittance is
  1.2 ?m
• ? Challenge of transverse emittance preservation
  in the injectors
• - PSBooster ejection ? 2.5 ?m
• - PS ejection ? 3 ?m
• - SPS ejection ? 3.5 ?m
• - LHC top energy ? 3.75 ?m

8
INTRODUCTION (6/13) ? LONGITUDINAL BEAM STRUCTURE

• The generation of the nominal bunch train for LHC
  (25 ns bunch spacing) is done in the PS

• Double-batch injection from PSBooster due to
  space charge in the PSBooster ? Rings 3-4-2-1-3-4
• Bunch splittings used instead of debunching /
  rebunching due to longitudinal microwave
  instability

Must be the 1st!
LHC Design Report, Ch. 7, p. 45
9
INTRODUCTION (7/13) ? SPS CHALLENGES
MKE kickers issues

• Impedance reduction programme in the SPS has made
  a major contribution to the ability of the SPS to
  produce the LHC beam
• Shielding of specific equipment, such as the
  magnetic septa, identified as an impedance source
• Shielding of some 900 intermagnet pumping ports
  has reduced significantly the resonant impedance
  in the machine and increased the stability of the
  LHC beam
• The nominal beam has successfully been
  accelerated to 450 GeV/c, despite the discovery
  that the electron cloud effect is a major issue
  for the SPS ? Continued machine development to
  understand and cure the phenomena in the SPS has
  been accompanied by additional studies using the
  SPS as a test-bed for the LHC. Periods of beam
  conditioning are now routinely used to scrub
  the surface of the vacuum chambers, reduce the
  secondary electron yield and minimise the vacuum
  pressure rise

10
INTRODUCTION (8/13) ? SPS BEAM PARAMETERS
Tolerance in bunch intensity? 10
Tolerance in trans. emittance? 20
Tolerance in long. emittance? 20
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INTRODUCTION (9/13) ? NOMINAL LHC FILLING SCHEME

• PS cycle length 3.6 s
• SPS cycle length 21.6 s
• LHC filling time (for the 2 rings) 8 min 38 s
  ( 12 SPS cycles of 21.6 s per beam ? 24 in
  total, i.e. a filling time of 24 ? 21.6 s 518.4
  s)

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INTRODUCTION (10/13) ? NOMINAL LHC BEAM IN THE
SPS IN 2004
3.3 ?1013 p at 450 GeV/c (i.e. 4 ? 72 288
bunches with 1.15?1011 p/b)
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INTRODUCTION (11/13) ? NOMINAL LHC BEAM IN THE
SPS IN 2006
3.6 ?1013 p at 450 GeV/c (i.e. 4 ? 72 288
bunches with 1.24?1011 p/b)
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INTRODUCTION (12/13) ? NOMINAL (LOW INTENSITY)
BEAM EXTRACTED FROM THE SPS IN 2007
Shown by S. Myers on 26/02/08 (AB meeting)
15
INTRODUCTION (13/13) ? NOMINAL (LOW INTENSITY)
BEAM EXTRACTED FROM THE SPS IN 2007
Shown by S. Myers on 26/02/08 (AB meeting)
16
THE LHC BEAM ZOO (1/4)
M. Benedikt, LHC-OP-ES-0002 rev 1.0 (2004)
Pilot safety beam

• Interest in the 50 ns variant has been
  resuscitated (since few months) to try and
  satisfy the need for low luminosity in IP2!

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THE LHC BEAM ZOO (2/4)
Needed before each physics coast
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THE LHC BEAM ZOO (3/4)
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THE LHC BEAM ZOO (4/4)
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MAIN SPS SUPERCYLE FORESEEN IN 2008 USER NAMES
(1/6)
26 GeV/c or acceleration up to 37 GeV/c

• SFTLONG1 (13 BP) CNGS1 (5) CNGS2 (5) CNGS3
  (5) LHCFAST1 (7) MD1/2 (5) 40 BP 48 s
• Later, when LHC is filling properly we will have
  to switch to an LHC filling supercycle

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MAIN SPS SUPERCYLE FORESEEN IN 2008 USER NAMES
(2/6)

• In 2007
• SPS timing user names changed to beam-type names
• At the same time we got the possibility via LTIMs
  to activate a given RF MMI stack for a given
  timing user ? Tended to 'decouple' the RF MMI
  stack name from the timing user name
• The BI settings are organized by beam type and
  can be loaded to any timing user ? This also
  decouples the BI settings from the timing user
  names
• In 2008 ? The idea is to go back to a given
  timing user associated to a certain SPS magnetic
  cycle more than to a certain beam type
• LHC1 LHC2 for nominal MAGNETIC LHC cycles
• LHCFAST1 LHCFAST2 for the short LHC MAGNETIC
  cycles
• LHCION1 LHCION2 for ion MAGNETIC cycles

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MAIN SPS SUPERCYLE FORESEEN IN 2008 USER NAMES
(3/6)
For the short magnetic cycles
24 in 2007
32 in 2008
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MAIN SPS SUPERCYLE FORESEEN IN 2008 USER NAMES
(4/6)

• ? Example of a Long MD cycle in 2008
• Timing user LHC1. LSA settings mapped to that
  user
• If we take a nominal beam on the cycle, RF MMI
  stack for LHC1 mapped to stack LHC25NS. BI
  settings for LHC-NOMINAL mapped to LHC1
• If we take a pilot beam on the cycle, RF MMI
  stack for LHC1 mapped to stack LHCPILOT. BI
  settings for LHC-PILOT mapped to LHC1
• 'Early' LHC filling SC with two fast LHC cycles.
  Cycles are mapped to timing users LHCFAST1
  LHCFAST2. LSA settings mapped to those users
• If we take a pilot beam on the 2 cycles, RF MMI
  stack for LHCFAST1 LHCFAST2 mapped to stack
  LHCPILOT. BI settings for LHC-PILOT mapped to
  LHCFAST1 LHCFAST2
• If we take an individual bunch on the 2 cycles,
  RF MMI stack for LHCFAST1 LHCFAST2 mapped to
  stack LHCINDIV. BI settings for LHC-INDIV mapped
  to LHCFAST1 LHCFAST2
• If we take 12 bunches (1 PSB ring) on the 2
  cycles, RF MMI stack for LHCFAST1 LHCFAST2
  mapped to stack LHC25NS. BI settings for
  LHC-NOMINAL mapped to LHCFAST1 LHCFAST2

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MAIN SPS SUPERCYLE FORESEEN IN 2008 USER NAMES
(5/6)
Different acceleration between NOMINAL and FAST
cycles
4320 (or 15120)
7590 (or 18390)
60 (or 10860)
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MAIN SPS SUPERCYLE FORESEEN IN 2008 USER NAMES
(6/6)
The (proton) LHC user names in the PS PSB
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ALTERNATIVE FILLING SCHEME!
SOME PROCEDURES REFERENCES FOR THE NOMINAL (4 ?
72 BUNCHES) BEAM
To see how things vary in this case
FILLING PATTERN (1/3)
NOMINAL FILLING SCHEME!
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4 ? 72 bunches
FILLING PATTERN (2/3)
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5 ? 48 bunches
FILLING PATTERN (3/3)
58
115
172
229
9
9
9
9
Batch 5
48
48
48
48
48
1.2 s
1.2 s
1.2 s
1.2 s
1.2 s
570
285
855
1140
29
PROCEDURE TO SET UP THE INJECTION (1/4)

• Check that the PS is not in simulated frequency

6 BPM of TT2 4 BPM in TT10

• TT10 BP settings

Last 10 BPM of TT10
Couplers with logarithmic amplifiers in TT10 ? No
gain
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PROCEDURE TO SET UP THE INJECTION (2/4)

• Injection kickers settings

The first 3 kickers can give until 11 ?s,
whereras the 4th one gives 2.5 ?s
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PROCEDURE TO SET UP THE INJECTION (3/4)
32
PROCEDURE TO SET UP THE INJECTION (4/4)
33
PROCEDURE TO SET UP THE MACHINE TRANSVERSALLY
(1/13)
ENERGY MATCHING PROCEDURE
- Inject the beam. Adjust BSPS till the first
turn is centered - Switch on RF (if not already
done) - Measure the orbit (about 100 ms after
injection) - Check the position at which the
beam is captured If the beam is not centered,
(that means the energy in the PS is such that
the revolution period in the SPS does not
correspond to the RF frequency in the SPS),
adjust BSPS till the beam is centered after
capture - The first turn is then no longer
centered - BPS should be adjusted (so as to
adjust the beam energy). - An excel spreadsheet
can be used to determine by which amount BPS
should be changed
34
PROCEDURE TO SET UP THE MACHINE TRANSVERSALLY
(2/13)

• Tunes (measured) ? To avoid slow beam losses from
  resonances (ecloud, space charge tune spreads)
• SPS Control  ? SPS Beam Control ? New Trim editor
  
• Qx ? 26.13
• Qy ? 26.185
• When there are more than 1 injection, Qx
  increases with the intensity and Qy decreases
  with the intensity (Laslett tune shift) ? One has
  to compensate for this effect
• In order to keep the coherent tune constant the
  Qx settings need to be decreased by 0.008 in
  correspondence of every injection and Qy must be
  increased by 0.005
• ? Jorg added in 2007 a menu in the MultiQ to
  correct the tune shift for each injection GO in
  the 'Tools' menu (main program toolbar) and check
  the box 'Show LHC beam "Injection Q"....'. This
  will make the appropriate menu/DV plot
  appear/disappear

35
PROCEDURE TO SET UP THE MACHINE TRANSVERSALLY
(3/13)

• Chromaticities (measured) ? To stabilize the beam
  with respect to the instabilities due to single
  bunch (effects from electron cloud)
• SPS Control  ? SPS Beam Control ? New Trim editor
  
• ?x ? 0.2
• ?y ? 0.4
• BEWARE DO NOT TRIM THE RADIAL STEERING BEFORE
  THE LAST INJECTION (even for chromaticity
  measurements). This would change the RF frequency
  we are sending to the PS - and the 40 and 80 MHz
  cavities will not like it!!! The radial position
  can be trimmed after the last injection
• Octupoles settings ? To achieve a machine as
  linear as possible
• SPS Control  ? SPS Beam Control ? New Trim editor
  
• H - 1 m-4 (Settings are not critical, but they
  shouldn't be too high ? Not larger than about 1
  m-4)
• V 0

36
PROCEDURE TO SET UP THE MACHINE TRANSVERSALLY
(4/13)

• Transverse dampers ? The transverse dampers are
  essential in the horizontal direction in order to
  damp the instabilities due to coupled bunches
  (effects from electron clouds and resistive
  wall). In the vertical plane they are mainly used
  to damp resistive wall instability
• Gain (for the nominal beam)
• Horizontal 23 dB
• Vertical 15 dB
• For 1 bunch or 12 bunches OFF
• For 72 bunches ? There are 2 pairs of transverse
  dampers per plane. They should be ON during the
  whole cycle

37
PROCEDURE TO SET UP THE MACHINE TRANSVERSALLY
(5/13)

• Timings ? SPSOP CCM ? Working Set ? RF-SPEC ?
  SPSRF7
• Switching on timings
• "tdamper h1 on opera"
• "tdamper h2 on opera"
• tdamper v1 on opera
• tdamper v2 on opera"
• Settings
• Timings defined with respect to event
  SIX.F1KFO-CT
• Coarse delay 995 ms (? i.e. 5 ms before 1st
  injection)
• Switching off timings
• "tdamper h1 off opera"
• "tdamper h2 off opera"
• tdamper v1 off opera
• tdamper v2 off opera"
• These should always be ENABLED
• Settings
• Timings defined with respect to event
  SIX.F1KFO-CT
• Coarse delay 20000 ms

Forewarning 1000 ms before first occurence of
injection
OFF timing should be a few ms after the timing
of the standard dump
38
PROCEDURE TO SET UP THE MACHINE TRANSVERSALLY
(6/13)

• MOPOS settings

39
PROCEDURE TO SET UP THE MACHINE TRANSVERSALLY
(7/13)
40
PROCEDURE TO SET UP THE MACHINE TRANSVERSALLY
(8/13)
Averaging over 5 orbits
41
PROCEDURE TO SET UP THE MACHINE TRANSVERSALLY
(9/13)
BEAM DUMP SETTINGS
42
PROCEDURE TO SET UP THE MACHINE TRANSVERSALLY
(10/13)
TT2 / TT10 LINE
May be not the latest optics!
43
PROCEDURE TO SET UP THE MACHINE TRANSVERSALLY
(11/13)
Max ?y QD ODD number
Max ?x QF EVEN number
SPS RING
?? ? 90º
SPS transverse tune ? 6 ? (18 / 4) 27!
? Qx ? 26.13 and Qy ? 26.18
44
PROCEDURE TO SET UP THE MACHINE TRANSVERSALLY
(12/13)
TI2
45
PROCEDURE TO SET UP THE MACHINE TRANSVERSALLY
(13/13)
TI8
46
PROCEDURE TO SET UP THE MACHINE LONGITUDINALLY
(1/13)

• RF loops
• PHASE LOOP (measures the difference between the
  phase of the RF and the phase from the beam and
  tries to minimize it)
• SYNCHRO LOOP ? We stay always on the synchro loop
  instead of going at some point on the radial loop
  for acceleration (we cannot do this with the FT
  beams because transition is crossed)
• BTRAIN is enabled at the beginning the ramp and
  switch off at the end of the ramp (Bup and Bdown
  are 0.1 Gauss)

47
PROCEDURE TO SET UP THE MACHINE LONGITUDINALLY
(2/13)

• 200 MHz TWC
• Feedforward (not used on FT beam) 1-turn delay
  feedback together (send correction to the cavity
  through a transmitter) ? To combat the beam
  loading
• Long. feedback (called also damper) ? Used since
  the injection, and then the gain is adjusted
  (high gain around the injections for injection
  damping), to combat coupled-bunch instabilities
• Injection into 2 MV bucket (mismatched)
• 800 MHz TWC
• Bunch shortening mode

Matched voltage is lt 1 MV
48
PROCEDURE TO SET UP THE MACHINE LONGITUDINALLY
(3/13)

• Timings
• At - 425 ms RF ON (TWC200)
• Phase loop ON (fprog) synchro loop ON
• 4 injections
• Before TWC 800 ON in bunch shortening mode after
  the 4th inj. Now it is ON already from the
  beginning due to the MKE kickers
• Max Bdot 0.35 T/s
• At 270 GeV/c, longitudinal blow-up done with
  phase modulation on 200 MHz (to have the shortest
  bunch length on the flat-top, otherwise one has
  coupled-bunch instabilities). It is active for
  100-200 ms, with an efficient time of 10-20 ms
• ?L 0.45 eVs at the end of the flat-bottom and
  it is 0.6-0.7 eVs on the flat-top
• Synchro with LHC
• Adiabatic voltage to send the shortest bunch
  lengths

49
PROCEDURE TO SET UP THE MACHINE LONGITUDINALLY
(4/13)
? Example of bunch length with nominal (4?72
bunches) beam but low intensity ( 2.5E13 p)
V200MHz 104 V
Full (4?) bunch length ns/100
V800MHz 103 V
Beam momentum GeV/c
Must enter in the LHC 2.5 ns bucket
50
PROCEDURE TO SET UP THE MACHINE LONGITUDINALLY
(5/13)

• Injection frequency
• - Value 200.264550 MHz ? injection B field
  1170.3 Gauss)
• - Setting SPS Control ? SPS Equipment Control ?
  SPS RF
• ? SPS RF Control ? RF Synchro ? Injection B field
  
• ? select appropriate MMI target (MD1, or LHC25ns,
  ...)
• ? Write 1170.3 Gauss (corresponds to 200.264550
  MHz)

• Injection pulses ? Sets the delay on top of the
  prepulse sent by
• the PS machine, in bucket number
• - Value 5500
• - Setting SPS Control ? SPS Equipment Control ?
  SPS RF ? SPS RF Control ? RF Synchro ? Injection
  pulses
• ? select appropriate MMI target  (MD1, or
  LHC25ns, ...)
• ? Write 5500

51
PROCEDURE TO SET UP THE MACHINE LONGITUDINALLY
(6/13)

• Injection bucket selector ? Defines where the
  beam is placed
• in the SPS (bucket number for 1st bunch in 1st
  batch)
• - Value 3881 for first batch, 3881 400 ?
  (n-1) for the nth batch
• - Note this value could change from one day to
  the
• other in first turn, check that the first batch
  is placed
• in the right place
• - Display
• - SPS Control ? SPS Beam Measurements ? Mountain
  Range
• - The bunch should be in the centre

52
PROCEDURE TO SET UP THE MACHINE LONGITUDINALLY
(7/13)

• Measurement
• SPS Control ? SPS Beam Measurements
• ? LHC First Bunch Bucket Error
• This application measures the error with respect
  
• to the injection bucket selector. It should be 0.
  
• If not correct the injection bucket selector by
  the
• appropriate amount (indicated by the application
  modulo 4620).

53
PROCEDURE TO SET UP THE MACHINE LONGITUDINALLY
(8/13)

• Setting
• SPS Control ? SPS Equipment Control
• ? SPS RF ? SPS RF Control ? RF Synchro ? Inj.
  bucket selector
• ? select appropriate MMI target (MD1, or LHC25ns,
  ...)
• ? Write ...

54
PROCEDURE TO SET UP THE MACHINE LONGITUDINALLY
(9/13)

• Injection phase ? When there is a change of
  injection bucket,
• there might be a small injection phase error.
• The bunches will oscillate in the first few
  turns.
• The phase loop will try to correct this effect
  quickly.
• Value 99 (Note This value can change from one
  day to another )
• Display
• SPS Control ? SPS Beam Measurements ? Mountain
  Range
• Some oscillations would be visible in the
  mountain range
• display
• Trouble shooting the bunch should be well
  centered at 11 ns.
• If it is off by 2.5 ns (half a bucket) the
  "injection phase" is
• wrong by 180 degrees.
• If it is off by 5 ns (one bucket) it is the
  "injection bucket
• selector" which is wrong by one unit

55
PROCEDURE TO SET UP THE MACHINE LONGITUDINALLY
(10/13)

• OASIS
• ? Connect global ? SPS ? RF LHC Loops
• If there is an offset, one should increase the
  injection
• phase accordingly (about 1 degree per 10 mV
  offset)
• Setting
• SPS Control ? SPS Equipment Control ? SPS RF
• ? SPS RF Control ? RF Synchro ? Injection phase
• ? select appropriate MMI target (MD1, or LHC25ns,
  ...)
• ? Use only the 1st injection
• ? Write ...

56
PROCEDURE TO SET UP THE MACHINE LONGITUDINALLY
(11/13)
57
PROCEDURE TO SET UP THE MACHINE LONGITUDINALLY
(12/13)

• Phase sampling
• Value 3480
• Setting
• TWC 200 MHz Low level 
• ? Phase Loop ? PL Cycle Select
• ? select appropriate MMI target  (MD1, or
  LHC25ns, ...)
• ? Phase sampling
• ? Parameter set number 2
• BU Bunch 3480

58
PROCEDURE TO SET UP THE MACHINE LONGITUDINALLY
(13/13)

• B start ?This is the timing at which RF switches
  to the frequency
• program (following changes in magnetic field)
• MTG event "SX.ST-RAMP-CTM" enabled and set to
  10860 ms
• SPSOP CCM ? Working Set ? RF-SPEC ? SPSRF6
• "pLHC frequency program b pulses on"
• Settings
• Timing defined with respect to event
  SX.S-RAMP-CT
• (start of the ramp)
• Delay is 0
• "pLHC frequency program b pulses off"
• Settings
• Timing defined with respect to event
  SX.S-SFLATTOP-CT
• (end of flat top)
• Delay is 30

59
MEASURING BEAM PARAMETERS (1/12)

• Transverse emittance
• In the PS
• Fast Wire Scanners (2 H with Dx ? 0 2 V)
• In the TT2-TT10 transfer line
• SEM wires SEM grids ? Without PS bunch rotation
  (otherwise meas. perturbed by ecloud!)

60
MEASURING BEAM PARAMETERS (2/12)
61
MEASURING BEAM PARAMETERS (3/12)

• OTR (Optical Transition Radiation)
• 4 in TT10 1 in TT2
• Measurements can be performed without SPS
  injection
• At least 3 OTRs required for a measurement

62
MEASURING BEAM PARAMETERS (4/12)

• In the SPS (SPS Control / SPS beam measurement /
  SPS wire scanner)
• Rotational Wire Scanner (6 m/s) 2 pairs in LSS4
  2 pairs in LSS5
• Linear Wire Scanner (1 m/s) 2 pairs in LSS5
• ? DO NOT USE the Linear Wire Scanners as these
  will burn with this high intensity beam (should
  be used for the LHC pilot bunch)

Should be preferred
Should be preferred
LINEAR
63
MEASURING BEAM PARAMETERS (5/12)
64
MEASURING BEAM PARAMETERS (6/12)
65
MEASURING BEAM PARAMETERS (7/12)

• IPM H (BIPMH51634) and V (BIPMV51734)

MD CYCLE
Gaussian of constant normalized emittance in blue
?x 2.68 mm
? Fanny is currently writing a program to have
the IPM measurement operational in 2008
?x 1.51 mm
66
MEASURING BEAM PARAMETERS (8/12)

• Longitudinal emittance
• In the PS
• Tomoscope (should be preferred) or BSM
• In the SPS
• By measuring the bunch length as a function of
  the RF voltage ? An application will be available
  to compute this (Fanny)

• Intensity
• In the PS
• BCT gives the total intensity (of the 72 bunches)
  
• BSM gives the relative bunch by bunch intensity
• Transfer line ? (SPS Control / SPS beam
  measurement / SPS FBCT)
• 1 FBCT at the beginning of TT2 1 FBCT at the
  end of TT10
• Absolute intensity, bunch by bunch
• Possibility to superimpose the measurements
  obtained with 2 different FBCTs

67
MEASURING BEAM PARAMETERS (9/12)

• In the SPS
• FBCT (Fast BCT) ? 1 (SPS Control ? SPS beam
  measurement ? SPS FBCT)
• Absolute intensity, bunch by bunch
• Possibility to superimpose the measurements
  obtained with two different FBCTs
• Normal BCTs ? 3
• 2 for high intensity (DBCTHIGH1 and DBCTHIGH3).
  From 1010 p up to a few 1013 p)
• 1 for low intensity (DBCTLOW4). From 108 p up to
  a few 1011 p)
• There is a difference of about 10 between the
  FBCT and the normal BCTs. The normal BCT is used
  for calibrating the FBCT
• Use one of the 2 high intensity BCTs (DBCTHIGH1
  or DBCTHIGH3)

68
? EXAMPLE OF EVOLUTION OF THE BCT FAST BCT
(10/12)
NOMINAL 4 ? 72 bunches
ALTERNATIVE 5 ? 48 bunches
BCT 5?1010 p
V200MHz 104 V
V800MHz 103 V
Beam momentum GeV/c
69
MEASURING BEAM PARAMETERS (11/12)

• Bunch length
• In the PS
• BSM
• In the SPS
• Application in BA3 Fanny
• Momentum spread ? Deduced from measurements of
  bunch length and longitudinal emittance (deduced
  from bunch length and RF voltage)

70
MEASURING BEAM PARAMETERS (12/12)

• Transverse tunes and chromaticties
• In the PS
• Qmeter Bernards application
• In the SPS
• Jorg released in 2007 a totally re-factored
  MultiQ application for the SPS based on the BBQ
  system (The old BOSC Qmeter system is no longer
  supported)
• Jorg also implemented in 2007 an automatic
  measurement of the chromaticity (linear and/or
  nonlinear) in the AutoQ ? It is AutoQprime

71
EXTRACTION (1/2)

• Once at 450 GeV/c the following actions take
  place during the flat-top, which is approximately
  1 second long
• Ramping of the extraction elements (magnetic
  septa and closed orbit bumpers) ready for
  extraction
• Fine re-phasing of the SPS with respect to the
  LHC in order to inject into the LHC at the
  required azimuthal position
• Compression of the bunch length by an RF voltage
  increase
• Cleaning of the tails of the beam distribution
  down to 3-3.5s by means of fast scrapers
• The status and settings of various elements of
  the LHC, the transfer lines, the SPS and the
  extraction channel must be surveyed and checked
  before extraction is permitted

72
EXTRACTION (2/2)

• MKE extraction kickers
• LSS4
• LSS6

73
CHANGES WHEN SWITCHING FROM FT TO
(High-intensity) LHC

• During (the scrubbing run and) the LONG MDs with
  LHC beam the ZS are RETRACTED / HV to 0 kV / ION
  TRAPS ON (inform the ZS expert). The cooling
  circuit for the septa magnets (circuits 214, 414
  and 614) should be switched OFF (by TI). Block
  the fast vacuum valves OUT in the injection and
  extraction areas (LSS1,LSS2,LSS6)
• Equipment modifications for the MD
• Changed accelerator mode for FT no extraction
• NORTH extraction off
• MST/MSE girders retracted
• Servo off
• Switched off TT20 AUXPS

74
REMAINING ISSUES IN 2008

• TIDVG outgassing
• Problem (only) when the beam is repeatedly
  dumped at high energy (450 GeV/c) with the
  nominal LHC beam ? We then have after few minutes
  an interlock on the downstream MKP (to prevent it
  from sparking) ? It is a problem in fact of
  vacuum and not dump!
• This is issue is currently under study
• MKDV1 outgassing
• The nominal LHC beam cannot be extracted to the
  LHC if we dont find a solution!
• During the 2007 MD we removed the last voltage
  step (which reduces the bunch length at the very
  end before going to the LHC) to allow the beam to
  go to 450 GeV/c otherwise it would not have been
  possible
• L. Ducimetiere informed us that nothing was done
  on this during the 2007-2008 shutdown

75
(LEAD) IONS (1/2)
76
(LEAD) IONS (2/2)
In the SPS in 2007
2007 MDs ? 90 of the design intensity (4?9E7?82)
with transverse emittances (rms, norm) 25
smaller than design (0.9 ?m instead of 1.2 ?m in
both planes)
? No ions in the SPS in 2008!