CERN
LIU Project Document No.
LIU-LHC-
CH-1211 Geneva 23
Switzerland
CERN Div./Group or Supplier/Contractor Document No.
TE/ABT
the
EDMS Document No.
LHC
Injectors
Upgrade
-
project
Date: 2005-04-04
Functional Specification
DRAFT 2.0
SPECIFICATION FOR KICKER SYSTEMS FOR
2.0 GeV PSB TO PS BEAM TRANSFER
Abstract
As part of the LIU project the extraction kinetic energy of the PSB will be increased from
1.4 to 2.0 GeV. This gives an increase in the beam rigidity of a factor of 1.30,
accompanied by a reduction in the physical beam size by a factor 1.14.
The purpose of the present document is to specify the requirements for upgrade of the
BE.KFA14L1 PSB extraction kickers, the BT.KFA10 and BT2.KFA20 recombination line
kickers, and the PI.KFA45 PS injection kicker.
The key kicker parameters of ∫B.dl, rise time, fall time, flat-top length and flat-top
ripple are defined, together with the justifications for the values.
Prepared by :
Wolfgang BARTMANN TE/ABT
Jan BORBURGH TE/ABT
Brennan GODDARD TE/ABT
Simone GILARDONI BE/ABP
Klaus HANKE BE/OP
Giovanni RUMOLO BE/ABP
Luc SERMEUS TE/ABT
Rende STEERENBERG BE/OP
Checked by :
Alfred BLAS BE/RF
Etienne CARLIER TE/ABT
Heiko DAMERAU BE/RF
Laurent DUCIMETIERE TE/ABT
Thomas KRAMER TE/ABT
Bettina MIKULEC BE/OP
Hannes BARTOSIK BE/ABP
Approval Group Members:
(to add)
Approval Group Leader:
Malika MEDDAHI TE/ABT
LIU Project Document No.
LHCPage 2 of 9
History of Changes
Rev. No.
Date
Pages
Description of Changes
1.0
11/11/14
Draft version 1.0 created
2.0
09/12/14
Version 2.0 including some comments
LIU Project Document No.
LHCPage 3 of 9
1. SCOPE
This document specifies the parameters for the kickers used for the beam transfer between
the PSB and the PS, in the context of the LIU upgrade project. The document:
 describes the motivation for the upgrades;
 outlines the existing kicker systems;
 describes the relevant PSB and PS beam parameters, for all beams;
 specifies the performance requirements including tolerances;
 describes the timeline.
The document does NOT describe the technical solutions which will be used to meet these
requirements – so for instance the option of augmenting the KFA45 strength with a second
KFA53 kicker is not explicitly covered. The detailed technical implementation will form the
subject of separate engineering specifications for the individual systems, based on the need
to meet the requirements in this document.
2. INTRODUCTION
The increase of the PSB extraction energy from 1.4 to 2.0 GeV is one of the cornerstones of
the LIU project [1], and will enable the limitation in intensity due to the space-charge tune
shift in the PS to be overcome [2]. The extraction systems of the PSB, the recombination
beamlines and beam transfer elements, and the injection system of the PS will all need to
function at the new higher beam energy.
2.1 MOTIVATION FOR KICKER UPGRADE
The kicker systems in the PSB extraction, BT recombination lines and PS injection all need to
provide 30% more ∫B.dl, to allow the transfer of the 2.0 GeV beam with a rigidity of
9.28 Tm. At the same time, the rise and fall times of the kickers must be compatible with the
required bunch lengths and filling schemes for the HL-LHC era beams, and with the present
specifications for the beams for other fixed-target users in the PS complex and the SPS.
The driver for the upgrade is the LIU nominal 25 ns beam, and the most important
parameters to respect are those required for this beam. Clearly, the changes to the kickers
should also not degrade the performance available for the SFTPRO beams for the higher
intensity, larger emittance beams used for other users than LHC. Finally, alternative (backup)
solutions for LHC such as the BCMS beam [3] may take advantage of the upgraded baseline
parameters, but should not define the extreme limits of the parameter space.
3. PSB TO PS BEAM TRANSFER AND KICKER SYSTEMS
The transfer from PSB to PS is shown schematically in Figure 1.
3.1 EXTRACTION FROM PSB
The BE.KFA14L1 kicker ejects the beam from the PSB. The rise time must be short enough to
fit into the shortest gap between the two longest bunches. Note that the PS harmonic number
determines this shortest gap, and not the PSB harmonic number. The flat-top length is
approximately one PSB turn, minus the rise time. The fall time is not constrained.
LIU Project Document No.
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3.2 RECOMBINATION OF THE 4 PSB RINGS
The two BT.KFA10 kickers each recombine two of the PSB rings into a single beamline. The
rise time must be short enough to fit into the shortest gap between the two longest bunches.
Note that the PS harmonic number determines this shortest gap, and not the PSB harmonic
number. The flat-top length must be approximately one PSB turn, minus the rise time.
The BT2.KFA20 kicker recombines the two beams thus generated – the rise time specification
is the same, but the flat-top length approximately twice as long. For both recombination
kicker types KFA10 and KFA20 the fall time is not constrained.
3.3 PS INJECTION KICKER
The PI.KFA45 kicker injects the beam into the PS. The rise time must be short enough to fit
between the two longest bunches on the highest PS operational harmonic (h=9). The flat-top
length is approximately four PSB turns. The fall time needs to be similar to the rise time (in
fact it is constrained by the h=8 bunch spacing and length as there is no missing bunch in the
PS bunch train).
Figure 1. Schematic of beam transfer between PSB and PS, illustrated for the HL-LHC BCMS
scheme (top), and the SFTPRO high intensity beams (bottom). Note that the order of PSB
rings injected into the PS always follows “3 before 4 before 2 before 1”. This means that the
fall times of the recombination kickers are never critical.
LIU Project Document No.
LHCPage 5 of 9
4. PSB AND PS BEAM PARAMETERS
While rise and fall times “short as possible” are clearly tempting to specify, it is crucial to
define the actual system requirements in view of the beam types planned for the HL-LHC era
after LS2. The rise/fall times are key parameters along with gap field, and affects strongly
the technical choices, cost and performance of the planned upgrades, plus the overall
feasibility and risk, in the context of many simultaneous activities with limited resources.
The bunch lengths and gaps between bunches in the two machines are a function of the
harmonic numbers, of the beam momentum and also of the beam type (intensity and
longitudinal emittance/RF voltage).
To alleviate the space charge limitations in the PS, the LHC type beams will be transferred at
2.0 GeV with the maximum possible bunch lengths. This reduces the lengths of the RF
buckets, due to the slight reduction in revolution periods with higher relativistic .
The option of 1.4 GeV beam transfer is also explicitly retained, and the aperture design of the
injection elements needs to accept the larger physical emittances at the lower energy. For
completeness the parameters are specified also at this beam momentum.
The PSB will operate at h=1 with long bunches for the nominal LHC beams, with h=2 for the
high-intensity Fixed Target beams, and at h=1 for the low emittance BCMS beams [3]. The
h=1 operation requires 2 injections into the PS (double-batch transfer), while h=2 operation
requires only a single injection into the PS (single batch transfer).
4.1 BASIC PSB AND PS BEAM PARAMETERS
The basic PSB and PS beam parameters relevant for the PSB-PS beam transfer for 1.4 GeV
and 2.0 GeV are given in Tables 1 and 2, respectively.
Table 1. 1.4 GeV PSB and PS beam parameters for PSB-PS beam transfer
Parameter
Value
Beam kinetic energy [GeV]
1.4
Beam rigidity [T.m]
A
PSB revolution period [ns]
B
PS revolution period [ns]
7.14
571
2286
Table 2. 2.0 GeV PSB and PS beam parameters for PSB-PS beam transfer
Parameter
Beam kinetic energy [GeV]
Beam rigidity [T.m]
A
PSB revolution period [ns]
B
PS revolution period [ns]
Value
2.0
9.28
552
2210
LIU Project Document No.
LHCPage 6 of 9
4.2 BUNCH LENGTHS AND DERIVED KICKER RISE, FALL AND FLAT-TOP TIMES
The set of parameters for the PSB-PS beam transfer kickers for 1.4 GeV and 2.0 GeV transfer
are given in Tables 3 and 4, respectively. Values are rounded to the nearest ns. Note that 6
bunches are injected into h=7 for the nominal LHC beam production scheme, while 8 bunches
are injected into h=8 for fixed-target type beams, and 8 bunches into h=9 for the LHC high
brightness BCMS beam.
Importantly, for h=2 the bunches in the PSB are not equally spaced – the fundamental RF
frequency is also used to modulate the bunch spacing prior to extraction, to fit the PS
harmonic number. This means that the rise time available for the PSB kicker depends on the
difference between the PSB revolution period and the PS bunch spacing, and so is shorter for
lower harmonic number in the PS.
Table 3. 1.4 GeV bunch lengths and derived parameters for PSB-PS beam transfer kickers
1.4 GeV
Basic
parameters
Bunch lengths
Rise times
Fall times
Flat tops
C
D =B/C
E
F=A-D
G
H
=A-G
=F-H
=D-G
=D-H
=D-G
= D x (1 + C - E) - G
= D x (1 + C - E) - H
=G
=D+H
=G
=D+H
=D+G
=3xD+H
=3xD+H
= D x (E - 1) + H
Parameter
PS harmonic number
PS bunch spacing [ns]
PS bunches filled
PSB 2nd spacing on h2 [ns]
Bunch length h1 [ns]
Bunch length h2 [ns]
PSB extr h1 [ns]
PSB extr h2 [ns]
Recomb h1 [ns]
Recomb h2 [ns]
PS inj h1 [ns]
PS inj h2 [ns]
PS inj h1 [ns]
PS inj h2 [ns]
PSB extraction h1
PSB extraction h2
Recomb 10. h1
Recomb 10. h2
Recomb 20. h1
Recomb 20. h2
PS injection h1
PS injection h2
7
327
6
244
223
140
348
104
104
187
104
430
513
222
467
223
467
550
1120
1120
1773
Value
8
286
8
285
170
170
401
115
116
116
116
116
116
170
456
170
456
456
1027
1027
2170
9
254
8
317
150
150
421
167
104
104
104
358
358
150
404
150
404
404
912
912
1928
LIU Project Document No.
LHCPage 7 of 9
Table 4. 2.0 GeV bunch lengths and derived parameters for PSB-PS beam transfer kickers
2.0 GeV
Basic
parameters
Bunch lengths
Rise times
Fall times
Flat tops
Label
C
D =B/C
E
F=A-D
G
H
=A-G
=F-H
=D-G
=D-H
=D-G
= D x (1 + C - E) - G
= D x (1 + C - E) - H
=G
=D+H
=G
=D+H
=D+G
=3xD+H
=3xD+H
= D x (E - 1) + H
Parameter
PS harmonic number
PS bunch spacing [ns]
PS bunches filled
PSB 2nd spacing on h2 [ns]
Bunch length h1 [ns]
Bunch length h2 [ns]
PSB extr h1 [ns]
PSB extr h2 [ns]
Recomb h1 [ns]
Recomb h2 [ns]
PS inj h1 [ns]
PS inj h2 [ns]
PS inj h1 [ns]
PS inj h2 [ns]
PSB extraction h1
PSB extraction h2
Recomb 10. h1
Recomb 10. h2
Recomb 20. h1
Recomb 20. h2
PS injection h1
PS injection h2
7
316
6
236
205
125
347
111
111
191
111
426
506
205
441
205
441
521
1072
1072
1704
Value
8
276
8
276
165
165
387
111
111
111
111
111
111
165
441
165
441
441
994
994
2099
9
246
8
306
135
135
417
171
111
111
111
356
356
135
381
135
381
381
872
872
1854
5. KICKER PERFORMANCE REQUIREMENTS
Using the data in Tables 3 and 4 the main performance requirements for the different PSPSB beam transfer kicker systems are summarised in Table 5. Note that the voltages
specified are required ones, for the existing system magnet configuration, and not
necessarily compatible with the system maximum operational voltages, specified rise
times or flat-top ripple.
All rise and fall times are given as 1-99 % values, which like the limits for the ripple on
the flat-top, are empirically derived. At present it is assume that the transverse damper
for the PS [4] is NOT used to damp injection oscillations. The damper may eventually
provide more margin for longer bunches to be injected into the PS, at a future date.
LIU Project Document No.
LHCPage 8 of 9
Table 5. Main PS-PSB beam transfer kicker system performance requirements [5, 6]
Parameter
Unit
Value
BE.KFA14
BT.KFA10
BT2.KFA20
PI.KFA45
Nominal kick angle
mrad
7.19
8.57
5.41
4.3
Max. kick angle
mrad
7.83
8.8
5.6
4.4
Max. Beam rigidity
T.m
9.28
9.28
9.28
9.28
Max. ∫B.dl (2 GeV)
T.m
0.073
0.082
0.052
0.041
Magnetic length
m
1.76
1.548
1.548
0.884
Max. gap field (2 GeV)
T
0.041
0.052
0.033
0.046
1.4 GeV Rise time
ns
104
104
104
104
2.0 GeV Rise time
ns
111
111
111
111
1.4 GeV Fall time
ns
-
-/-
-/-
116
2.0 GeV Fall time
ns
-
-/-
-/-
111
1.4 GeV Flat-top length
ns
467
467
1120
2170
2.0 GeV Flat-top length
ns
441
441
1072
2099
Flat-top ripple (peak)
%
±2
±2
±2
±2
Timing jitter (peak)
ns
±1
±1
±1
±2
The following important points are to be noted:
 The maximum 135 ns bunch length for the 2.0 GeV BCMS scheme (injecting 8b
into h=9 with h=2 in the PSB) at 2.0 GeV is defined by the 111 ns rise/fall time
limits for the recombination kickers and the PS injection kicker rise time;
 The 111 ns fall time limit for the PS injection kicker is defined by the 8b into h=8
in PS for the SFTPRO beam, and limits the bunch length for the SFTPRO beam at
2.0 GeV to 165 ns. This will still represent an important increase in the
performance potential for this beam compared to 170 ns at 1.4 GeV;
 Importantly, the fall times for the BT.KFA10 and BT2.KFA20 kickers are not
relevant, and can be long, as the order in which the different PSB rings are
recombined is never changed;
 If needed (for example if the PFL cables are eventually consolidated) the present
PSB extraction kicker pulse length of 1600 ns can be reduced significantly. The
maximum length required for extracting h2 at 1.4 GeV is 467 ns. 1 PSB turn at
1.4 GeV is 571 ns. So, there is absolutely no need for pulse flat-top length longer
than ~600 ns.
 The present BT.KFA10 recombination kicker pulse length of 1600 ns could also be
reduced significantly. The maximum length required for combining h2 at 1.4 GeV
is 467 ns.
 The present BT2.KFA20 recombination kicker pulse length of 3000 ns could also
be reduced significantly. The maximum length required for combining h2 at
1.4 GeV is 1120 ns.
 The present PI.KFA45 injection kicker maximum pulse length of 2600 ns could be
reduced somewhat. The maximum length required for injecting h2 at 1.4 GeV is
2170 ns.
LIU Project Document No.
LHCPage 9 of 9
6. SCHEDULE
The upgraded kicker systems need to be in installed and commissioned at the latest in
LS2, at the end of the LIU project, to be ready for beam commissioning at the start of
LHC Run3.
7. REFERENCES
[1] reference to LIU TDR
[2] reference to PS tune shift brightness limitation
[3] reference to BCMS beam scheme
[4] reference to PS injction damper specification
[5] K.-D. Metzmacher, L. Sermeus, The PSB Ejection and Recombination Kicker Systems for
LHC, CERN
[6] K.-D. Metzmacher, L. Sermeus, The PS injection Kicker KFA45 Performance for LHC,
PS/PO/Note 2002-015 (Tech.), CERN PS Division