LIU Ions crash program meeting
(October 30th, 2015)
https://indico.cern.ch/event/458938/
Present:
S.Albright (BE-RF)
R.Alemany (BE-OP)
J.Axensalva (BE-OP)
H.Bartosik (BE-ABP)
A.Blas (BE-RF)
M.Bodendorfer (BE-ABP), scientific secretary
M.Gazior (BE-BI)
D.Quartullo (BE-RF)
S.Gilardoni (BE-APB), Project leader LIU Ions, chairman
S.Jensen (BE-CO)
A.Huschauer (BE-ABP)
V.Kain (BE-OP)
D.Manglunki (BE-OP), Deputy project leader LIU Ions
M.Meddahi (TE-ABT), Project leader LIU
S.Pasinelli (BE-OP)
G.Tranquille (BE-BI)
M.Meddahi opens the meeting at 16:00h.
A status report of the respective work package holders follows:
Beam dynamics studies on LEIR (H.Bartosik, A.Huschauer, V.Kain)
Main points of the presentation:
 Continued with “getting to know the machine” using MDNOM with 5
injections.
 Continued development of online tools
 Investigations of signals of transverse and longitudinal pickups (Freddy)
 Work on the electron cooler settings (Gerard)
Status & outlook I:
 Machine optics and control
 Studies on RF capture
 Beam instrumentation
 Space charge and losses at RF capture
 Instabilities and transverse feedback
 Studies on electron cooler
 Optimization of injection process
Discussion.

V.Kain reports that none of the LEIR quadrupoles or dipoles are in LSA. To be
investigated.

A.Blas asks about radial offset before but close to RF-capture. S.Gilardoni
replies that with Argon ion beam it made no difference whether the beam is
dragged in p-space or by the RF-capture.

M.Meddahi asks about decay curve of intensity. S.Gilardoni refers to general
lifetime behavior due to limited vacuum qualities.

R.Alemany asks about integrating the new chromaticity information into the
cycle generation. A.Huschauer cautions this action because he believes that
the action of the orbit knob at injection and at the electron cooler has an
influence on the chromaticity measurement, this would make the integration
rather complicated and obscure for the LEIR operator.

J.Axensalva reports that the additional Schottky timer not yet implemented
due to absence of expert.

H.Bartosik points out the importance of the ionization profile monitor signals
and the associated post processing. He wants this as a high priority task for
the coming weeks.
Electron cooler MD in LEIR (G.Tranquille)
G.Tranquille reports about the electron-cooler focused machine development
study in LEIR. The cycle used featured 2 injections, separated by 200ms. The
ratio of control voltage to grid voltage equal to 0.3 has produced a hollow
electron beam. Changing this ratio from 0.3 to 0.2 has produced a less hollow
electron beam.
He further reports that increasing the electron beam from 200mA to 420mA did
not bring forth the desired effect of shortening the cooling time of the lead ion
beam in LEIR. This needs further investigation because in the past the increase in
electron beam current has always lead to a decrease in cooling time.
A test was setup to measure the time required to decrease the control voltage
enough in order to stop electron cooling of the lead ion beam at a desired point
in cycle time. The test has revealed that the electron beam was not switched
quick enough and that the lead ion beam has been dragged in momentum space
significantly before electron cooling and momentum dragging has stopped.
G.Tranquille investigates a new type of control circuit in order to shorten this
critical voltage drop time, which is required to switch off the electron beam
before the lead ion beam is dragged in momentum space significantly.
D.Manglunki as when the new upgraded circuit can be operational. G.Tranquille
replies that the new and upgraded circuit could be operational by December
2015. He adds that A.Frassier would be able to carry out the circuit upgrade
within one morning.
H.Bartosik points out that an orbit trim has been implemented to control and
modify the closed orbit in the electron cooler.
V.Kain asks about MDNOM behavior with respect to the electron cooler.
G.Tranquille replies that the new settings with higher electron beam current
have not yet been used on the MDNOM cycle.
H.Bartosik asks how sensitive the alignment of the ion beam and electron beam
is. S.Gilordoni replies that never noticed a big difference in LEIR has been
observed between situation where the ion beam was correctly co-aligned with
the electron beam and situations where the electron beam was not correctly coaligned with the ion beam. He suggests a scan with the newly implemented orbit
knob, which controls the closed orbit in the electron cooler, in order to observe
the cooling efficiency during the scan. G.Tranquille adds that the electron beam
features a diameter of 4.2cm.
G.Tranquille comments that with Argon beam in 2015, we have seen an inverse
proportionally quicker beam cooling effect with an increased electron beam
current.
G.Tranquille reports a bad vacuum quality measured near the vertical beam
ionization profile monitor. He refers to the recently observed decay in beam
intensity during a LEIR cycle. M.Meddahi states that this needs to be investigated
further.
Losses in LEIR at capture (A.Blas)
Main points of the presentation:





Betatron activity absent. None observed.
No betatron lines observed.
No sign of synchrotron dipolar activity.
Cavity is non-linear -> suspects Tomoscope to be non-precise.
Details about RF-cavity gap return and self-bunching.
Neither the transverse feedback nor the RF beam control main loops are to be
suspected when losses occur during capture. This conclusion is based on
measurements made with different PUs that show no trace of dipolar
synchrotronic, nor H and V betatron excitation. A betatron excitation decay time
measurement will be carried out to further convince the LIU Ion LEIR crash
program team.
The noise appearing at the output of LL-RF is still to be analyzed but is also not a
candidate to explain the losses as it is only likely to cause emittance blow-up
(keeping in mind that losses occurs already during the injection plateau where
beam out of the RF bucket would still remain in the vacuum chamber and thus
not counted as losses).
The dirty capture can possibly be due to an uneven un-bunched beam structure
(to be checked), but this is not likely to be the source of losses, as again losses
occur also during the injection plateau where the particles ejected out of the
bucket will not be counted as losses.
This week A.Blas will analyze the progression of the beam length and height
together with the progression of the RF voltage to check this blow-up issue (he
will keep the tomoscope out of the loop for now as the RF voltages are not really
as supposed by the tomoscope)
The observed “microwave” instability will also be tackled, although he doesn’t
believe it can cause losses on the injection plateau.
He will also try to use a flat cycle at the injection energy with a single harmonic
RF to allow for a better decomposition of the different observations
Summary:
From the RF measurements standpoint, the incoherent effects have a better
chance to be the source of the problem… this is kind of supported by Simone’s
comment on the important direct space charge encountered at injection energy.
Discussion:


M.Meddahi asks whether the beam can be excited, lost and then being
observed by the TWFB system. A.Blas says that this was not done yet.
M.Meddahi demands experimental proof showing that this can be observed.
A.Blas agrees to deliver experimental proof.
M.Meddahi suggests continuing the investigation next week. Does the system
do what it is designed to do? A.Blas agrees to carry out TWFB MD with
destructive excitation of the ion beam and subsequent signal analysis.
Further planning:
S.Gilardoni explains the planning for next week and the week after next week.
Link to Excel sheet. A.Blas comments that he will need time slots of at least 1h for
non-ppm actions. S.Gilardoni associates Tuesday morning and Thursday
morning for these MDs. To be confirmed.
R.Alemany reports that she has started to look at creating a LEIR cycles from
scratch. The identifies two options for the LEIR cycle generation:
1. All code in LSA with generation framework. However, she has realized that
the LEIR parameters are not straightforward by definition and that there are
many individual settings.
2. Template cycles (by G.Kruk). These template cycles would be protected from
manipulations and would serve as a base for the process to generate new
cycles.
Furthermore, she points out the large number of different parameters
hampering the implementation of the straightforward cycle generation process.
Next meeting: Friday Nov. 6th, CCC glass box at 16:00h.
M closes the meeting at 17:34h.