first collision of bepcii
DESCRIPTION
First Collision of BEPCII. C.H. Yu May 10, 2007. Methods of collision tuning Procedures and data analysis Luminosity and background Summary. Methods of collision tuning. 22mrad Horizontal crossing angle. Designed β function and beam size @IP : - PowerPoint PPT PresentationTRANSCRIPT
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First Collision of BEPCII
C.H. YuMay 10, 2007
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• Methods of collision tuning• Procedures and data analysis• Luminosity and background• Summary
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Methods of collision tuning
Designed β function and beam size @IP :β x* / β y*= 1.0m / 1.5cm x* / y*= 0.4mm / 5.5m
Designed backup scheme (without SCQ) β function and beam size @IP :β x* / β y*= 2.0m / 5cm x* / y*= 0.5mm / 12.2m
Beam size from beam-beam scan fitting result @IP :x* / y*= 0.5mm / 16m
e- e+
22mradHorizontal crossing angle
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-0.002-0.001
00.001
0.002Horizontal Offsetm
-0.001
0
0.001Vertical Offsetm
-0.04
-0.02
0
0.02
0.04
V kick anglerad-0.04
-0.02
0
0.02
0.04
V kick anglerad
-0.002-0.001
00.001
0.002 HorizontalOffsetm
-0.001
0
0.001
VerticalOffsetm
-0.02
0
0.02
H kick anglerad-0.002
-0.0010
0.0010.002 HorizontalOffsetm
-0.001
0
0.001
VerticalOffsetm-3 -2 -1 0 1 2 3
-0.02
-0.01
0
0.01
0.02
-10 -5 0 5 10
-0.04
-0.02
0
0.02
0.04
Methods of collision tuningBeam-Beam kicker
Bassetti-Erskine formula
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Before collision commissioningSoftware preparation According to the design of BEPCII IRBPM accuracy test Select BPM for the collision tuningIP 4-bump program and strength correction IP orbit resolution and stability Reduce 4-Bump orbit leak less than 3%Discuss luminosity issues with detector people
Methods of collision tuning
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IP 4-Bump for collision tuning ( orbit leak < 3% )Methods of collision tuning
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BESIII detector is located in south of storage ring.
Methods of collision tuningCollision tuning items
Beam separation at NCP
Longitudinal position tuning
Crossing angle tuning
Transverse position tuning
Luminosity optimization
NCP
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Procedures and data analysis
For the consideration of injection rate, vertical local bump was set mainly by BER. The vertical separation between e+ e- beams at NCP is about 5mm ( ~5x )。
Vertical beam separation at North Crossing Point (NCP)
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Longitudinal position tuning The distance from the IP to R4CBPM00 is 0.6587m.
According to the signal of the R4CBPM00, relative timing of two beams was adjusted by shifting RF phase so that two beams collide at the nominal IP.
R4CBPM00 Accuracy 3mm R3CBPM00
Procedures and data analysis
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Procedures and data analysis
Transverse position tuningVertical crossing angle
The vertical crossing angle was measured through RF phase scan. If the vertical crossing angle exists, the vertical offset of two beams will be changed in the horizontal scan. Therefore, the crossing angle can be detected by observing the vertical beam-beam deflection RF phase scan.
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Procedures and data analysisTransverse position tuning
Horizontal offset and vertical offset
Scan: e- IP bump height Monitor: e+ IR BPMMax. H. kicker angle 0.049mrad & V. kicker angle 0.076mrad @ 3mA*3mA
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Procedures and data analysisTransverse position tuning
Horizontal offset and vertical offset
Same results if we Scan: e+ IP bump height Monitor: e- IR BPMTransverse offset and vertical crossing angle were removed by local 4-
bump.
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Horizontal offset scan Vertical offset scan
First collision of BEPCII
Mar. 25, 2007
The scan step of Horizontal IP bump and vertical IP bump are 10um and 2um respectively 。
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Procedures and data analysis
IP coupling tuning
r1, r2, r3 and r4 at the IP can be adjusted independently. Coupling parameters tuning is a effective and important Luminosity optimization.
T and M is 44 one-turn transfer matrix in the physical system and normal system.
ICCI
MM
ICCI
Tv
u
0
0
1
43
21
rrrr
C
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Procedures and data analysis
y* waist tuning
The y* waist scan is realized by fitting the strength of a set of quadrupoles(Q2, Q3, Q4, Q5, Q6, Q7, Q8 and Q9) which are all located beside the IP. function waist tuning is a effective and important method for Luminosity optimization.
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Luminosity and backgroundTune shift measurement
Tune shift can be observed clearly.
At May 8 day shift5mA*5mA collision horizontal tune shift is 0.014 and vertical tune shift is 0.012.
1-2-29*
34 scm105)(
)()()1(1017.2 cm
AIkGeVERLy
bby
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Luminosity and backgroundBlowup phenomenon
Normal collision case Blowup caseSometimes blowup phenomenon appeared during collision scan.
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Luminosity and backgroundLuminosity Detectors
Old BaBar detector used in BEPC
Zero degree photon detecore+ e- e+ e-
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Luminosity and backgroundBLM data with horizontal offset scan
0
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-2 -1. 5 -1 -0. 5 0 0. 5 1 1. 5 2 2. 5 3 3. 5e+ hori zontal bump hei ght @I P(mm)
Lumi
nosi
ty c
ount
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-3 -2. 5 -2 -1. 5 -1 -0. 5 0 0. 5 1 1. 5 2 2. 5 3
e- hori zontal bump hei ght @I P(mm)
Lumi
nosi
ty c
ount
BLM is a sensitive detector to monitor the situation of beam collision. The e+ horizontal orbit near the IP affect BLM background obviously. Usually we scan e- orbit for collision orbit optimization while keep e+ orbit unchanged.
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Luminosity and backgroundBLM data with vertical offset scan
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-0. 1 -0. 075 -0. 05 -0. 025 0 0. 025 0. 05 0. 075 0. 1
e- vert i cal bump hei ght @I P(mm)
Spec
ific
lumi
nosi
ty
0
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-0. 2 -0. 15 -0. 1 -0. 05 0 0. 05 0. 1 0. 15 0. 2
e+ vert i cal bump hei ght @I P(mm)
Spec
ific
lumi
nosi
ty
BLM works well. Both e+ and e- vertical orbit near the IP are not sensitive to the BLM background.
ebebb IIN
L
__
y LuminositSpecific
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Luminosity and backgroundOld BEPC BaBar luminosity detector
Some device tuning works have been done. The background of the BEPC detector is very sensitive to both e+ and e- orbit in the IR. Luminosity value is still under study.
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Summary
Collision tuning methods have been tested successfully in BEPCII 。 Beam instrument system 、 IP bump magnets 、 power supply system 、 control system can satisfy precision collision orbit scan 。 However, there are still a long way for us to reach the designed luminosity goal.