Minutes of the LIU ions crash study
meeting on November 19, 2015
Agenda (https://indico.cern.ch/event/462618/)
1. Beam dynamics studies
2. Discussion on the operational use of both RF cavities
3. AOB
Present: S. Albright, J. Axensalva, H. Bartosik, A. Blas, C. Carli, S. Gilardoni, S. Jensen, V. Kain, D. Küchler,
A. Huschauer, D. Manglunki, M. Meddahi, S. Pasinelli, D. Quartullo, G. Rumolo
1. Beam dynamics studies (H. Bartosik, A. Huschauer, V. Kain)
H. Bartosik presented an overview of last week’s activities. Emphasis was put on setting up the
BIOMD cycle, which has a length of four BPs, in order to increase the accumulated intensity. The next
step after copying and adjusting the settings from MDNOM was to correctly adjust the B-train offset
(ER.TRAIN). Therefore, the RF capture was advanced and the beam was centered while keeping the
FREVCORR at zero. Attention has to be paid, as these settings crucially affect the TFB.
Furthermore, it was reported that the beam performance seems to depend on the previously played
LEIR user and the accumulation on BIOMD was significantly improved after putting NOMINAL in front
instead of EARLY. D. Manglunki mentioned that EPC will profit from a planned beam stop of half an
hour on Friday afternoon to investigate ETL.BHN10, as the corresponding sampler shows an
important ripple at 50 Hz on this device. To understand the effect of the different users on each other,
all settings should be homogenized. H. Bartosik added that the chromaticity on EARLY had not been
changed so far and, therefore, the settings of the sextupoles are significantly different than on
NOMINAL and MDNOM. Furthermore, the cycle following NOMINAL or BIOMD seems to be degraded
as well. Magnetic measurements of ETL.BHN10 were suggested to fully understand its behavior. C.
Carli reminded that even if the correction of the injection efficiency takes place with ETL.BHN10, a
different element could actually cause the problem. D. Manglunki suggested to check ITE.BHN40 as
well, as it is the only PPM element in that line. The transfer line settings could also be made completely
non-PPM, but this would obviously cause troubles if changes were required during an MD.
H. Bartosik continued by presenting a screenshot of the MATLAB LEIRmonitor, showing 13 injections
on BIOMD, a maximum accumulated intensity of 9 x 1010 charges and a maximum intensity of 6.65 x
1010 charges on the flat top. During the last injections the setting of the horizontal tune is critical,
which hints to a space charge related effect. Therefore, it will be necessary to investigate the
transverse shape of the beam with the IPM in order to compute the variation of the Laslett tune shift
along the cycle. A. Huschauer added that currently only up to two seconds can be acquired with the
IPM. J. Axensalva replied that this was a known issue and that L. Jensen is looking into a problem
with the FESA class causing this issue. J. Axensalva furthermore reported the availability of the timing
ER.BGI-START, which can be used to shift the start of the IPM acquisition.
C. Carli confirmed that also in the past losses were observed to critically depend on the working point,
but rather after capture and that twice the intensity of NOMINAL was accumulated in the past using a
special coast mode. The vacuum at that time was apparently better than today and the life time was
less affected. D. Manglunki informed that investigations of the vacuum are planned during the YETS
and S. Gilardoni suggested to try to reactivate the NEGs before opening the machine.
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Minutes of the LIU ions crash study
meeting on November 19, 2015
The FREVCORR was observed to start at a non-zero value on all users, which potentially also leads to
malfunctioning of the TFB. M. E. Angoletta fixed this issue. D. Manglunki enquired whether the loss at
capture could be related to this fact and whether the loss currently occurs at capture or at the start of
the ramp. H. Bartosik replied that with the current setup of BIOMD, losses appear only at the
beginning of the ramp.
The improved performance of BIOMD causes the intensity trace to be no longer visible on the LEIR
vistar. An offline discussion was suggested to search for possibilities of adjusting the intensity gain,
maybe even depending on the user.
H. Bartosik presented observations related to the Schottky spectrum. Depending on the settings of the
e-cooler, the beam systematically disappears from the measured spectrum after about five injections.
C. Carli explained that come coherent signal could perturb the acquisition and, therefore, one should
look at the signal in time domain. D. Manglunki stated that some Schottky spectra should be
measured, stored and made available for the different observations.
Further studies to understand the effect of the TT2 and PS stray fields on the LEIR injection efficiency
were launched. So far, no strong dependence of the injection performance on either of this parameters
was found and studies will continue next week.
2. Discussion on the operational use of both RF cavities (all participants)
Triggered by the fact that an increase of the RF voltage increased the transmission, the question was
raised whether both FINEMET cavities could be used operationally at the same time. D. Manglunki
mentioned that this was due to a limit on the amplifiers rather than on the cavities themselves. Prior to
the meeting, M. E. Angoletta had stated that additional development of the DLLRF would be required.
S. GIlardoni reported that, according to C. Rossi, both cavities can already be used for MDs; however,
it should be officially requested at the IEFC. Also because the FINEMET material could suffer from
erosion. For the future, one could profit from the development in the PSB to improve the cavities. A.
Blas reminded that any possible impedance issue due to the additional cavity should be taken into
account and enquired whether the beam size was compared to theoretically computed values of the
acceptance to justify the increase of voltage. S. Gilardoni replied that due to the coupling to the
transverse plane increased voltage might not only be beneficial in terms of longitudinal dynamics but
also in terms of transverse space charge.
D. Manglunki added that the optimum situation would be to implement more powerful amplifiers to
keep one cavity as an operational hot spare of the other.
M. Meddahi asked if any measures could be foreseen already now to use both cavities and A. Blas
replied that he could think of some non-permanent fix, which would have to be discussed with M. E.
Angoletta.
3. AOB
S. Gilardoni mentioned that the transmission of the high-intensity cycle should be investigated in the
SPS in the period between December 3rd and 14th, after the stop of the north area programed when the
LHC is filled. D. Manglunki added that the source will be refilled after the stop of the north area.
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Minutes of the LIU ions crash study
meeting on November 19, 2015
D. Küchler reported that the current delivered by the source at the moment is even better than
nominal. After refilling the oven, it takes some time to find a good working point of the source and
adjustments have to be carried out slowly to avoid spoiling lead and decreasing the life time.
Apparently, the transmission in ITH has deteriorated since last September and those losses are
currently reducing the available current at the end of LINAC3. H. Bartosik added that the rematching
of the transfer line still has to be implemented after the north are run.
S. Gilardoni presented the planning for next week and asked D. Küchler to discuss with either R.
Scrivens or G. Bellodi concerning the reduced transmission in ITH.
D. Manglunki mentioned that the cycle using 12 injections into LHC should be finalized on Friday and
the operators should measure the emittances.
Minutes by A. Huschauer on November 25, 2015
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