rhic electron cloud and vacuum pressure rise characteristics
DESCRIPTION
The 13 th ICFA Beam Dynamics Mini-Workshop Beam Induced Pressure Rise in Rings. RHIC electron cloud and vacuum pressure rise characteristics. P.He, H.C.Hseuh, W.Fischer, U.Iriso, D.Gassner, J.Gullotta, R.Lee, L.Smart, D.Trbojevic, L.F.Wang and S.Y.Zhang. Outline. - PowerPoint PPT PresentationTRANSCRIPT
RHIC electron cloud and vacuum pressure rise characteristics
P.He, H.C.Hseuh, W.Fischer, U.Iriso, D.Gassner, J.Gullotta, R.Lee, L.Smart, D.Trbojevic, L.F.Wang and S.Y.Zhang
The 13th ICFA Beam Dynamics Mini-WorkshopBeam Induced Pressure Rise in Rings
Outline
Part I: Residual gas composition during RHIC pressure rise
Part II: Solenoid field effect on RHIC e-cloud
Accelerator Complex
G10G12
G8
G6G4
G2
Two type of pressure rises observed at RHIC 2003 run
*the beam transition pressure rise for ions
*the electron cloud induced pressure rise at the injection
The residual gas composition during multipacting and its evolution along the pressure rise is very helpful toward our
understanding in this critical issue
Gas Composition and its Evolution along the Pressure Rise(G2)-Beam
Transition Pressure Rise
H2
COH2O
1 min
More Concern about Gas Composition and its Evolution
along the Electron Cloud induced pressure rise at the injection
We will focus on that!
Gas Composition and its Evolution along the Pressure Rise(G2)
S.Y.Zhang
5 mins
Gas Composition and its Evolution along the Pressure Rise(G12)
H2 CO
H2O
Beam Intensity
CCG: 1e-10 to 1e-7 torr
10 mins
Gas Composition and its Evolution along the Pressure Rise(G4)
H2
CO
H2O
Beam Intensity
CCG: 1e-9 to 3e-7 torr
10 mins
Gas Composition and its Evolution along the Pressure Rise(G8)
H2
CO
H2O
Beam Intensity
CCG: 3e-11 to 1e-8 torr
10 mins
Residual Gas Spectrum, during multipacting
(CERN)
Different scale respect to the above figure, where peak 2(H2) and 28 have been omitted, to show the
behaviour of the peak 18(H2O)
H2
CO
H2O
CO230 mins
Extensive studies at CERN have shown that water vapour plays an important role in the contribution of the SEY. It is possible that the presence of water molecules increases the sticking probability for other gases.
In-Situ SEY Measurement
(CERN)
N.Hilleret
RHIC Installed 11 x 5.2m x 12cmΦ TiZrV coated pipes this summer
coated by SAES Getters with license from CERN
at Q3-Q4 with high P during d-Au runs
yo1, bo2, yi2(2), bi9(2), yi10(4), ip12
TiZrV NEG coating pipes
IR2
IR12
Solenoid, ~2 m
Cold cathode gauge - fast response
Ion pump/TSP/cold cathode gauge
yo1
bi1
bo2
yi2
yo12
bi12
1 3
4
5 6 7 8 9 10
2
4
1
3
6
5
pw3.
3
pw3.
2
pw3.
1
pw1
pwx
pwx
pw1
pw3.
1
pw3.
2
pw3.
3
bo11
yi11
RHIC Electron Detector Solenoid & NEG Pipe Locations19 September 2003L. Smart x2425
Numbers designate power supply
yi10bi9
Pin Diode
NEG Pipe
ED
New Components for 2004 Run
A. Rossi
NEG still pumping
H2
CO
CH4
Evidence of NEG saturation
A. Rossi
H2
CO
CH4
CO
H2
G12-PWXG12-PW1
G11-PW1G11-PWX
Run 2004: one NEG pipe at G11
RGA
CC Gauge
Comparison with Run 2003: no NEG pipe at G11
G12-PWXG12-PW1
G11-PWXG11-PW1
Beam Intensity
Run 2004: four NEG pipes at YI10
H2
CO
Enlarge this area
Beam IntensityCCG
RGA
RGA
CCG
Run 2004: two NEG pipes at YI2
RGA
CCG
Beam Intensity
Part I: Residual gas composition during RHIC pressure rise
Part II: Solenoid field effect on RHIC e-cloud
Noiselevel
Electron Energy Spectrum
Ubaldo
Solenoid Field Effect(1)-May 30L.Smart
CCG
Beam Intensity
CCG
Beam Intensity
Solenoid
ED
Solenoid Field Effect(2)-May 09
Cyclotron Resonance at RHIC?Cyclotron frequency does not match bunch spacing
-further study needed
Cyclotron Resonance
Condition
SLAC-PUB-9813
M.Pivi
B - Sweep during fill #3812. (N=1.5 •1010 p-pb).
Even at the maximum value of B, VED is only reduced by a factor of ~3 (not enough to fully suppress the cloud).~in RHIC we have ~7% solenoids covering,Maybe more solenoid needed in the future.
Solenoid Field Effect(3)
B can help to fully suppress the e-cloud during fill #3530. (N=1.1 •1010 p-pb).
PSR:
EC was reduced by a factor ~50 by ~20G solenoid field. However, there was no measurable effect on the instability threshold when weak solenoids covering ~10% of the ring circumference were excited.
R.Macek
Y. Suetsugu
KEK PF:
Non-uniform Solenoid Field (Opposite Polarity)
Uniform Solenoid Field(Equal Polarity)
0
0.2
0.4
0.6
0.8
1
0 20 40 60 80 100
Uniform Field
Non-uniform Field
Y. Suetsugu
Solenoid Field Effect(4)
From the simulation, we can see no electron in the center of the beam pipe if we use equal polarity solenoid field
Run 2004, RHIC solenoid in equal polarity
Solenoid at RHIC tunnel & Solenoid PS
Conclusions and Future Works
• Evidence that solenoid will help to reduce the electron cloud build up• Residual gas spectrum show electron stimulated desorption due to multipacting
• Improve electron detector design • Verify experimentally the effectiveness TiZrV NEG coating to reduce the electron cloud build up after activated at 250°C(max ~ 1.1) and also after saturation (max <1.2~1.3)
• More solenoid(~30%), more NEG pipes(~300m), in-situ SEY measurement