Transcript LIU - CERN Indico

Status of the open actions on the
PS injection kicker and septa
J. Borburgh, J. Abelleira, W. Bartmann, A. L. Ducimetiere, A. Ferrero, J. Jentzsch, T. Kramer,
M. Serluca, L. Sermeus, E. Urrutia
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PS injection outstanding
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GFR for bumpers defined. Functional
specification to be formalised once bump
orbit is finalised.
Low β quads to be specified in functional
specification.
PS injection septum SRR: separate SRR for
septum (TE/ABT) and for transformers
(TE/EPC) to be issued.
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Septa aperture verification
The remote displacement range of the septa was
verified, using a previous version of the beam
orbit for:
Max. IN position; 50 mm, 9 mrad
Nominal position; 52 mm, 12 mrad
Max. OUT position; 64 mm, 16 mrad
New MU 41 / 42 vacuum chambers were
assumed.
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Case 1 Max. in position
Injected beam (orange)
Bumped beam (yellow)
Orbiting beam (purple)
Case 2: Nominal position
Injected beam (orange)
Bumped beam (yellow)
Orbiting beam (purple)
Case 3: Max. out
Injected beam (orange)
Bumped beam (yellow)
Orbiting beam (purple)
Clearance of bumper @ Max. Out
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PS injection kicker KFA45
It is proposed to upgrade the existing system.
Outstanding items from last LIU-PS meeting:
1. Repeat the simulation with the longer value of
bunch (224 ns bunch).
2. Repeat the simulation with the bunch in the middle
of the ripple.
3. Repeat the emittance growth measurements in PS
for a better understanding of the discrepancy
between the simulation and the measurements.
4. Prepare risk assessment and planning for upgrade
LIU-PS meeting 20/10/2015
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LIU model of SC mode (as
presented last time)
1. Check maximum length bunches
327 ns bunch spacing, 223 ns bunch length (see Kicker specs)
Assume Gaussian bunch, measurements look more uniform
2. Check what happens if a bunch is hit by
the short-circuit reflection
Moved kicker delay such that core of bunch 2 is centrally placed on the waveform
3. Emittance measurements vs. simulations
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Very difficult to measure the
emittance of LHC beams in
the PS
Setup: 2 BPs, kick with 2nd
batch inj on extraction flattop;
measure before and aftter kick
Strong non Gaussian tails for
strong kicks
At least 40% less measured
than expected theoretically
 numbers shown from
theoretical calculation are
conservative; gives an idea
which part of the waveform is
affecting most the beam
quality
LIU-PS meeting 20/10/2015
Relative small error bar on
measurements
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Conclusions (1/2)
• As discussed last time, the emittance growth values are calculated analytically and seem
pessimistic compared to measurements in the machine.
• The analytic results can be used to compare effects from rise/fall/ripple between different
kicker waveforms.
Emittance growth in %
Flattop ripple
Rise/fall edges
Postpulse ripple
LIU upgrade field
0.4
1.0
1.7
Measured current
present system
0.1
1.7
7.7
Simulated current
LIU upgrade
0.3
1.3
1.3
Recap from
last meeting
• Moving bunch 2 centrally on the SC reflection increases the emittance growth from about
0.5% to about 2.5%
• Increasing the bunch length to the maximum value assumed for the upgrade
• Did not assume bunch shape from measurements but Gaussian
• Bunches 2 and 3 not affected as expected
• Bunch 1 and 4 show an increased emittance growth of 2-3%
4. KFA 45 Proposed System Modifications
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Studies on Pspice models indicate that the following measures will bring the kicker pulse within
specification:
Requirements Simulation
Margin
a) Module dephasing optimization,
b) Removing part of the LEMO ferrites,
𝑇𝑟𝑖𝑠𝑒
105 𝑛𝑠
𝟖𝟑 𝐧𝐬(✓)
20%
c) New Ferrites at magnet entrance box,
𝑇𝑓𝑎𝑙𝑙
105 𝑛𝑠
𝟗𝟎 𝐧𝐬(✓)
14%
d) Fixed SC with LC filter,
Ripple
±2%
±1.1%(✓)
45%
e) Slight modification of DS termination load.
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Studied since last meeting
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System improvements have been simulated individually
(to have a reference for measurements during YETS).
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Integration of ferrites in magnet entry box has been
studied -> new (stretched) entry box is necessary, hence
only possible during EYETS.
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Sensibility analysis for new SF6 cables has been
performed (Impedance tolerance needs to be better than
0.5 Ohm)
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Possibility to run in terminated mode with some of the
improvements for SC mode has been studied (ripple
degrades from 0.6% to 1.1%).
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Overview of Implementation
Proposed
Improvement
Material
needed
Where
Cost
factor
Validation test
Reversible?
Residual Implementation
Risk
Optimized
dephasing
Cable and
LEMO
connectors (on
stock)
B.365
low
YETS (needs all 4
modules available
in SC mode)
Y (~1h)
low
(conventional cables)
Optimized
LEMO Ferrites
- (some ferrites
to be removed)
B.365
low
YETS
Y (~1d)
low
New ferrites at
magnet entry
box
Ferrites to be
prepared,
drawings, parts
to be
manufactured
Tunnel
medium
EYETS
Y (~1w)
medium
(Oil and SF6 gas circuit to be
opened, vacuum not affected)
Fixed SC
SC plug ( TEABT workshop)
Tunnel
low
YETS
Y during test
period, N
once finally
implemented
low (for YETS Only SC
Thyratron to be taken out and
replaced by plug for tests)
B.365
low
YETS
Y (~1d)
low
DS termination
load
optimization
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Schedule
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Before December 2015: Documentation ready
December 2015:
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Prepare parts for validation tests
Repair Module 1 & 2 SC mode
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January-February 2015: Implementation & Validation tests and
measurements
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End of YETS: hand system back in terminated mode (as before
YETS)
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Spring 2016: develop stretched magnet entry box
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EYETS: implementation of all improvements – go to fixed SC
mode but keep fall back options
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LS2: Remove fall back option (SC power supply and controls,
termination resistor, etc.)
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Conclusions (2/2)
For the KFA45 upgrade a planning is proposed,
aiming to:
• validate the approach during the YETS
2015-2016
• Implement the upgrade modifications in the
EYETS, keeping fall back solutions
• Remove fall back solutions in LS2
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