First tests with a 25ns “doublet” beam at the SPS injection
G. Iadarola, H.Bartosik, G. Rumolo
Many thanks to:
T. Argyropoulos, T. Bohl, S. Cettour Cave, H. Damerau, L. Kopylov , J. Esteban Muller,
F. Follin, S. Hancock, C. Lazaridis, Y. Papaphilippou, E. Shaposhnikova, M. Taborelli
Special thanks to all the SPS operator crew
LIU-SPS -BD meeting 22/11/2012
Outline
•
Why a scrubbing beam
•
Why “doublets”
•
Tests with single bunch in the SPS
•
Test with a bunch train
•
o
Effect on strip-detector signal
o
Effect on pressure along the ring
Conclusions and future studies
Outline
•
Why a scrubbing beam
•
Why “doublets”
•
Tests with single bunch in the SPS
•
Test with a bunch train
•
o
Effect on strip-detector signal
o
Effect on pressure along the ring
Conclusions and future studies
Why do we need a scrubbing beam?
0
2
Req. scrubbing dose [C/mm ]
10
What do we need?
-1
10
-2
10
-3
10
-4
10
-5
10
“Example” scrubbing curve from lab
-6
10
1
1.2
1.4
SEY
1.6
1.8
Why do we need a scrubbing beam?
0
2
Req. scrubbing dose [C/mm ]
10
What do we need?
-1
10
-2
10
-3
10
-4
10
-5
10
“Example” scrubbing curve from lab
-6
10
1
1.2
1
EC current (E e >50eV) [mA/m]
10
1.4
SEY
1.6
1.8
0
10
What do we have?
-1
10
-2
10
-3
10
MBB – 25ns beam
-4
10
1
1.2
1.4
1.6
1.8
Why do we need a scrubbing beam?
0
• The beam is still degraded due to EC
• The dose is not sufficient to continue
scrubbing in a reasonable time
2
What do we need?
-1
10
-2
10
-3
10
-4
10
-5
10
“Example” scrubbing curve from lab
-6
10
1
1.2
1
10
EC current (E e >50eV) [mA/m]
Possible issue:
Req. scrubbing dose [C/mm ]
10
1.4
SEY
1.6
1.8
0
10
What do we have?
-1
10
-2
10
-3
10
MBB – 25ns beam
-4
10
1
1.2
1.4
1.6
1.8
Why do we need a scrubbing beam?
0
• The beam is still degraded due to EC
• The dose is not sufficient to continue
scrubbing in a reasonable time
2
Possible issue:
Req. scrubbing dose [C/mm ]
10
-2
10
-3
10
-4
10
-5
10
“Example” scrubbing curve from lab
Possible solution:
10
• A “scrubbing beam” which exhibits a
10
-6
1
1.2
1
EC current (E e >50eV) [mA/m]
lower multipacting threshold
What do we need?
-1
10
1.4
SEY
1.6
1.8
0
10
What do we have?
-1
10
-2
10
-3
10
MBB – 25ns beam
-4
10
1
1.2
1.4
1.6
1.8
Why do we need a scrubbing beam?
0
• The beam is still degraded due to EC
• The dose is not sufficient to continue
scrubbing in a reasonable time
2
Possible issue:
Req. scrubbing dose [C/mm ]
10
-2
10
-3
10
-4
10
-5
10
“Example” scrubbing curve from lab
Possible solution:
10
• A “scrubbing beam” which exhibits a
10
• No need for acceleration
• No stringent requirements on beam
quality
-6
1
1.2
1
EC current (E e >50eV) [mA/m]
lower multipacting threshold
What do we need?
-1
10
1.4
SEY
1.6
1.8
0
10
What do we have?
-1
10
-2
10
-3
10
MBB – 25ns beam
-4
10
1
1.2
1.4
1.6
1.8
Outline
•
Why a scrubbing beam
•
Why “doublets”
•
Tests with single bunch in the SPS
•
Test with a bunch train
•
o
Effect on strip-detector signal
o
Effect on pressure along the ring
Conclusions and future studies
Why “doublets”?
The “simplest” idea would be to shrink the bunch spacing:
•
PS bunch rotation is designed “around” 40MHz  Not possible to inject
“bunch to bucket” with spacing shorted than 25ns
Why “doublets”?
The “simplest” idea would be to shrink the bunch spacing:
•
PS bunch rotation is designed “around” 40MHz  Not possible to inject
“bunch to bucket” with spacing less than 25ns
A “relatively easy” scheme could be to extract a 25ns bunch train with long bunches
(~10ns) and capture each bunch in two SPS buckets getting a 25ns “doublet” beam.
Why “doublets”?
Why should it work?
Beam prof. [p/m]
11
x 10
2
1.5
1
0.5
10
20
30
40
50
60
70
1.4
1.35
Ne / Ne (0)
1.3
Electron emission
1.25
Electron absorption
1.2
1.15
1.1
1.05
PyECLOUD simulation
1
10
20
30
40
Time [ns]
50
60
70
Why “doublets”?
Why should it work?
Beam prof. [p/m]
11
x 10
2
1.5
1
0.5
10
20
30
40
50
60
70
1.4
1.35
Ne / Ne (0)
1.3
1.25
1.2
Below the threshold the two
effects compensate each
other, no accumulation over
subsequent bunch passages
1.15
1.1
1.05
PyECLOUD simulation
1
10
20
30
40
Time [ns]
50
60
70
Why “doublets”?
Why should it work?
Beam prof. [p/m]
11
x 10
2
1.5
1
0.5
10
20
30
40
50
60
70
1.4
Shorter e-cloud decay
1.35
Ne / Ne (0)
1.3
More efficient
e-
production
1.25
1.2
1.15
1.1
1.05
PyECLOUD simulation
1
10
20
30
40
Time [ns]
50
60
70
Why “doublets”?
Why should it work?
Beam prof. [p/m]
11
x 10
2
1.5
1
0.5
10
20
30
40
50
60
70
1.4
1.35
Ne / Ne (0)
1.3
Accumulation between
subsequent turns
1.25
1.2
1.15
1.1
1.05
PyECLOUD simulation
1
10
20
30
40
Time [ns]
50
60
70
Simulation study
10
2
sey = 1.30
10
10
10
10
-2
-4
-6
1.1
1.15
1.2
0.8
0.6
0.4
Remarks:
Intensity per bunch of
the doublet (b.l. 4ns)
(b.l. 3ns)
0.2
1.25
0
•
0.60e11ppb
0.70e11ppb
0.80e11ppb
0.90e11ppb
1.00e11ppb
1.10e11ppb
1.20e11ppb
6btc 25ns
1.20e11ppb
0
Scrubbing current (50eV) [A/m2]
Scrubbing dose (50eV) [mA/m]
MBB - 26GeV 1
1.3
SEY
-0.02
1.35
1.4
-0.01
1.45
1.5
0
Position [m]
0.01
0.02
The doublet beam shows a lower multipacting threshold compared to the standard 25ns
beam if the intensity is larger than 0.8e11ppb (1.6e11ppb from the PS)
Simulation study
0.6
0.60e11ppb
0.70e11ppb
0.80e11ppb
0.90e11ppb
1.00e11ppb
1.10e11ppb
1.20e11ppb
6btc 25ns
1.20e11ppb
0.5
0.4
0.3
0.2
0.1
0
-0.02
-0.01
0.8
0.6
0.4
Remarks:
Intensity per bunch of
the doublet (b.l. 4ns)
(b.l. 3ns)
0.2
0
Position [m]
0.01
0.02
-0.02
-0.01
0
Position [m]
0
•
sey = 1.30
MBB - 26GeV 1
Scrubbing current (50eV) [A/m2]
Scrubbing current (50eV) [A/m 2]
sey = 1.30
0.01
0.02
The doublet beam shows a lower multipacting threshold compared to the standard 25ns
beam if the intensity is larger than 0.8e11ppb (1.6e11ppb from the PS)
•
The scrubbed region is smaller  to be used, with radial steering, as a last stage of the
scrubbing
Outline
•
Why a scrubbing beam
•
Why “doublets”
•
Tests with single bunch in the SPS
•
Test with a bunch train
•
o
Effect on strip-detector signal
o
Effect on pressure along the ring
Conclusions and future studies
Test with single bunch
On 25-26 Oct. a first test was carried out with a single bunch to test the capture
scheme:
•
Special PS cycle for a single 10ns long bunch was setup by PS experts
•
SPS cycle (Q26) with one injection + 1s flat bottom + acceleration to 32GeV
Test with single bunch
On 25-26 Oct. a first test was carried out with a single bunch to test the capture
scheme:
•
Special PS cycle for a single 10ns long bunch was setup by PS experts
•
SPS cycle (Q26) with one injection + 1s flat bottom + acceleration to 32GeV
ramp
Test with single bunch
On 25-26 Oct. a first test was carried out with a single bunch to test the capture
scheme:
•
Special PS cycle for a single 10ns long bunch was setup by PS experts
•
SPS cycle (Q26) with one injection + 1s flat bottom + acceleration to 32GeV
•
RF Voltage program has been optimized to maximize the capture
Test with single bunch
Main indications from these tests:
•
Max. capture (>95%) is obtained injecting on VRF≤1MV and increasing to
3MV after few ms
Test with single bunch
Main indications from these tests:
•
Max. capture (>95%) is obtained injecting on VRF≤1MV and increasing to
3MV after few ms
Test with single bunch
Main indications from these tests:
•
Max. capture (>95%) is obtained injecting on VRF≤1MV and increasing to
3MV after few ms
Test with single bunch
Main indication from these tests:
•
Max. capture (>95%) is obtained injecting on VRF≤1MV and increasing to
3MV after few ms
Thanks to C. Lazaridis
Test with single bunch
Main indication from these tests:
•
Max. capture (>95%) is obtained injecting on VRF≤1MV and increasing to
3MV after few ms
•
A dip in the voltage program, simulating a second injection, does not
significantly affect the transmission
Outline
•
Why a scrubbing beam
•
Why “doublets”
•
Tests with single bunch in the SPS
•
Test with a bunch train
•
o
Effect on strip-detector signal
o
Effect on pressure along the ring
Conclusions and future studies
Test with bunch train
On 15 Oct. a first test was carried out with a single bunch:
•
Special PS cycle for 72x(10ns long bunch) was setup by PS experts (up to
1.85ppb injected in the SPS)
•
Same SPS cycle as for single bunch test (to check capture)
•
Injecting with VRF=1MV and ramping to 3MV in 5ms
•
Damper OFF (setup to be done)  beam stabilized with high
chromaticity (ξx=0.5, ξy=0.35)
Test with bunch train
Remarks:
•
Still good capture
Test with bunch train
Increased chroma.
Remarks:
•
Still good capture
•
We can control slow losses with high chromaticity settings
Test with bunch train: beam profile
Beam profile along the cycle
2.2
2
1.8
1.6
Time [s]
1.4
1.2
1
0.8
0.6
0.4
0.2
0.2
0.4
0.6
0.8
Thanks to T. Argyropoulos and J. Esteban Muller
1
Time [ s]
1.2
1.4
1.6
1.8
Test with bunch train: beam profile
Beam profile along the cycle
2
2.2
2
1.5
Time [s]
1.8
1.6
Time [s]
1.4
1
1.2
0.5
1
0.8
0.6
0.15
0.16
0.17
0.18
Time [ s]
0.4
0.19
0.2
0.2
0.2
0.4
0.6
0.8
Thanks to T. Argyropoulos and J. Esteban Muller
1
Time [ s]
1.2
1.4
1.6
1.8
Test with bunch train: beam profile
Beam profile along the cycle
2
2.2
2
1.8
Time [s]
1.4
Time [s]
1.6
1.5
1
1.2
1
0.5
0.8
0.6
1.57
1.58
0.4
1.59
1.6
Time [ s]
1.61
1.62
0.2
0.2
0.4
0.6
0.8
Thanks to T. Argyropoulos and J. Esteban Muller
1
Time [ s]
1.2
1.4
1.6
1.8
Test with bunch train: beam profile
500cycle
Beam profile along the
2.2
450
2
400
350
1.8
300
Turn
1.6
Time [s]
1.4
250
200
1.2
150
1
100
0.8
50
0.6
0.15
0.16
0.4
0.17
0.18
Time [ s]
0.19
0.2
1.4
1.6
0.2
0.2
0.4
0.6
0.8
Thanks to T. Argyropoulos and J. Esteban Muller
1
Time [ s]
1.2
1.8
Test with bunch train
500 along the cycle
Beam profile
2.2
450
2
400
350
1.8
Time [s]
1.4
300
Turn
1.6
250
200
1.2
150
1
100
0.8
50
0.6
1.57
1.58
1.59
1.6
Time [ s]
0.4
1.61
1.62
0.2
0.2
0.4
0.6
0.8
Thanks to T. Argyropoulos and J. Esteban Muller
1
Time [ s]
1.2
1.4
1.6
1.8
Test with bunch train: beam profile
0.07
Beam profile along the cycle
0.06
2.2
0.05
Beam profile [a.u.]
2
1.8
1.6
Time [s]
1.4
1.2
0.04
0.03
0.02
0.01
1
0
0.8
-0.01
0.92
0.6
0.93
0.94
0.95
Time [ s]
0.96
0.4
0.2
0.2
0.4
0.6
0.8
Thanks to T. Argyropoulos and J. Esteban Muller
1
Time [ s]
1.2
1.4
1.6
1.8
Outline
•
Why a scrubbing beam
•
Why “doublets”
•
Tests with single bunch in the SPS
•
Test with a bunch train
•
o
Effect on strip-detector signal
o
Effect on pressure along the ring
Conclusions and future studies
Test with bunch train: EC strip detectors
MBA-like Stainless Steel liner
25ns “doublet”
(1.7e11p/doublet)
25ns standard
(1.6e11p/bunch)
Test with bunch train: EC strip detectors
MBB-like Stainless Steel liner
25ns “doublet”
(1.7e11p/doublet)
25ns standard
(1.6e11p/bunch)
Test with bunch train: EC strip detectors
MBB-like Copper liner
25ns “doublet”
(1.7e11p/doublet)
25ns standard
(1.6e11p/bunch)
Outline
•
Why a scrubbing beam
•
Why “doublets”
•
Tests with single bunch in the SPS
•
Test with a bunch train
•
o
Effect on strip-detector signal
o
Effect on pressure along the ring
Conclusions and future studies
Test with bunch train: pressure
72 “doublets”
Arcs
72 bunches
Arcs
Higher press. rise
Outline
•
Why a scrubbing beam
•
Why “doublets”
•
Tests with single bunch in the SPS
•
Test with a bunch train
•
o
Effect on strip-detector signal
o
Effect on pressure along the ring
Conclusions and future studies
Summary and proposals for future work
Summary:
•
A 25ns spaced train with 72 “doublets” can be produced in the SPS by
capturing 10ns long bunches into two SPS RF buckets
•
A clear enhancement on the e-cloud signal w.r.t. standard 25ns beam has
beam observed in the SPS strip detectors
•
Enhancement observed also on the pressure rise along the ring
Future work:
•
Transverse damper tests
•
Tests with more than one batch
•
Strategy for radial position displacement along future Scrubbing Runs (at
26GeV can be done with orbit correctors)
Thanks for your attention!