Upload
thi
View
39
Download
0
Embed Size (px)
DESCRIPTION
Preliminary summary of the LHC scrubbing run in LBOC , 11/12/2012 G. Arduini , H. Bartosik, G. Iadarola, G. Rumolo Thanks to the machine Coordinators, Cryogenics, Damper, EN/STI, Injection, Operation , Vacuum teams, ABP, RF and BI colleagues contributing to measurements. - PowerPoint PPT Presentation
Citation preview
Preliminary summary of the LHC scrubbing run
in LBOC, 11/12/2012G. Arduini, H. Bartosik, G. Iadarola, G. Rumolo
Thanks to the machine Coordinators,Cryogenics, Damper, EN/STI, Injection,
Operation, Vacuum teams,ABP, RF and BI colleagues contributing to measurements
Aims of the 2012 scrubbing run
• Further reduce the SEY over the whole machine– Use a 25ns beam at 450 GeV, monitoring electron cloud observables
and beam quality evolution– Eventually ramp to 4TeV up to a few hundreds of bunches (for
beam-beam, e-cloud, and UFO studies and for 25ns pilot run and additional scrubbing!)
• Collect additional information on the evolution on the SEY as a function of the accumulated electron dose (especially in the low SEY region) and compare machine data with existing models
– Essential to validate models and establish strategies for the post-LS1 era
• In parallel, learn about other possible differences in 25ns vs. 50ns operation (concerning heating, stability, UFOs)
Scrubbing Overview
• Fast intensity ramp-up and overall excellent machine availability
• Beam under control (damper, chromaticity, octupoles) in spite of the record intensities (up to 2.7x1014 p, 2748 bunches per beam)
IB1 IB2
Dam
per
sett
ing-
upIn
j. se
ttin
g-up
ALIC
E U
FO C
ryo-
regu
lati
on
MSR
8+cy
cle
Cryo
-reg
ulat
ion
MSR
8+cy
cle
TDI o
utga
ssin
g, C
ryo-
regu
lati
on
MSR
8+cy
cle
Inve
stig
atio
ns o
n bl
ow-
up+
POPS
Inve
stig
atio
ns o
n bl
ow-
up
Fills 3389 3407
Heat load evolution• The heat load on the beam screens was used on line for
estimating the efficiency of the scrubbing process
Thanks to L. Tavian
Heat load in sector 56
Main limitations
Smooth run, no fundamental showstopper was found Good scrubbing dose was maintained all along the scrubbing period.
The overall efficiency was determined by:• Vacuum pressure in the MKI region (during the initial
stages):o The interlock levels were gradually increased (tanks:
2∙10-9mbar 4∙10-9mbar, interconnects: 1∙10-8mbar 4∙10-8mbar)
• Cryogenics (with higher intensities):o Limited cooling power at stand alones in P6 and
8 required about 10’ between successive injectionso Try to dump the beams in conditions of lower heat
load (to avoid strong fluctuations on 120A current lead temperature precycle needed)
Other limitations• Vacuum pressures along the ring were continuously
monitored by the vacuum teamo Apart from MKIs and shortly ATLAS during the first
night, no significant slow down coming from pressure rises
Thanks to TE-VSC and EN-STI
Other limitations• Vacuum pressures along the ring were continuously
monitored by the vacuum teamo Apart from MKIs and shortly ATLAS during the first
night, no significant slow down coming from pressure rises
• TDIs had to be opened after each injection in order to keep heating and outgassing under control.
A. Lechner
Pressure runaway that triggered a manual dump
Other limitations• Vacuum pressures along the ring were continuously
monitored by the vacuum teamo Apart from MKIs and shortly ATLAS during the first
night, no significant slow down coming from pressure rises
• TDIs had to be opened after each injection in order to keep heating and outgassing under control.
A. Lechner
Other limitations• Vacuum pressures along the ring were continuously
monitored by the vacuum teamo Apart from MKIs and shortly ATLAS during the first
night, no significant slow down coming from pressure rises
• TDIs had to be opened after each injection in order to keep heating and outgassing under control.
o On 10/12 – last night of scrubbing – one jaw of the TDI in point 8 got stuck in open position (twice) The EN/STI piquet could remotely reset the motor
o LVDT reading of TDI.4L2 LU might trigger a warning/error, on the *LOWER* limit due to drift while cooling down. Access ongoing, exchange of one of LVDTs
Thanks to TE-VSC and EN-STI
Other limitations• Vacuum pressures along the ring were continuously
monitored by the vacuum teamo Apart from MKIs and shortly ATLAS during the first
night, no significant slow down coming from pressure rises
• TDIs had to be opened after each injection in order to keep heating and outgassing under control.
o On 10/12 – last night of scrubbing – one jaw of the TDI in point 8 got stuck in open position (twice) The EN/STI piquet could remotely reset the motor
o LVDT reading of TDI.4L2 LU might trigger a warning/error, on the *LOWER* limit due to drift while cooling down. Access ongoing, exchange of one of LVDTs
• No anomalous heating was observed on other sensitive elements (e.g. collimators) (larger bunch lengths and smaller bunch intensities)
Thanks to TE-VSC and EN-STI
Initially:• Transverse instability leading to beam dump
→ Injecting a single train of 72 bunches with chroma set to 2→ Injecting trains of 216 and 288 bunches, even with chroma set to
15!
Beam quality evolution
Thanks to R. De Maria,
W. Höfle, D. Valuch
During injection set up
Beam quality evolutionInitially:
• Transverse instability leading to beam dump → Injecting a single train of 72 bunches with chroma set to 2→ Injecting trains of 216 and 288 bunches, even with chroma set to
15!• Poor lifetime, however exhibiting signs of improvement
even within the same fillBeam 1 Fill 3389
Train spacing 3.7 ms 1 msTrains with 72 288 bunches
Beam 2
Q’ ~ 15 Q’ ~ 7
Q’ ~ 15 Q’ ~ 7
Beam quality evolutionBunch by bunch lifetime strongly improved within the first scrubbing fill (Fill 3389).
Filling scheme with minimum possible batch spacing and maximum number of bunches was employed for the following fills.
Between Friday Dec. 7th and Sunday Dec. 9th there were 10 scrubbing fills with more than 2000b. per beam.
Beam quality evolutionBeam lifetime (CCC monitoring)
Sunday 9 Dec
Thursday 6 Dec
Beam quality evolutionBeam lifetime – Fill 3390
Beam 1
Beam 2
Beam quality evolutionBeam lifetime – Fill 3390
Beam 1
Beam 2
Beam quality evolutionBeam lifetime – Fill 3398
Beam 1
Beam 2
Beam quality evolutionBeam lifetime – Fill 3398
Beam 1
Beam 2
Beam quality evolutionBeam lifetime – Fill 3405
Beam 1
Beam 2
Beam quality evolutionBeam lifetime – Fill 3405
Beam 1
Beam 2
Beam quality evolutionSummary of lifetimes
Scrubbing Scrubbing
Studies
Miscellaneous• Important transverse emittance blow up
→ Affecting only some bunches of the first injected train→ Seen with BSRT, confirmed with WS, both planes
• Effect suppressed by increasing the octupole strength from -0.5 to -2.0
Octupole setting -0.5
Octupole setting -2.0
Preliminary considerations• 3.5 days of scrubbing with 25ns beams at 450GeV were
carried out with high heat load (i.e. electron) rate
• e-cloud effects on the beam were visibly mitigated but not suppressed yet (seemingly confirmed by both heat load and beam lifetime measurements)
• Important information on the SEY evolution vs. electron dose collected for validation/improvement of our models and for enabling us to extrapolate to post-LS1 operation
• More data analysis (including transverse emittances from BSRT and stable phase shift) and interpretation ongoing + more information/additional scrubbing expected from MDs with ramps to 4 TeV
Thanks for your attention!