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pbar Yield and Collection Efficiency of the FAIR pbar Source. FAIR – CERN –FNAL pbar sources angular and momentum distributions after the target pbar collection with a magnetic horn MARS simulation of the system target – horn pbar collection with a Li lens summary.

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pbar yield and collection efficiency of the fair pbar source

pbar Yield and Collection Efficiencyof the FAIR pbar Source

  • FAIR – CERN –FNAL pbar sources
  • angular and momentum distributions after the target
  • pbar collection with a magnetic horn
  • MARS simulation of the system target – horn
  • pbar collection with a Li lens
  • summary
slide2

FAIR/CERN/FNAL pbar Sources

Increases the pbar yield by  50 %

Design goal: Luminosity for HESR experiments = 2 × 1032 cm-2s-1Max. pbar scattering cross section 100 mb (H2 target) → pbar consumption: 2 × 107 s-1cycle time 10 s (cooling time in the CR)overallpbar yield: 5 × 10-6 pbar/p (based on CERN data) → 4 × 1013 ppp (FAIR BTR)

FAIR Collector ring will be operated at h = 1, CERN ring was operated at h = 6

Time needed for stochastic cooling in CR (AC), upgrade possible

K. Knie, [email protected], 4.12.2007

overview
Overview

29 GeV p from SIS 100

pbar separator240 p mm mradp = 3.82 GeV/cDp/p = 3%

target +collector

K. Knie, [email protected], 4.12.2007

pbar distribution after the target
pbar Distribution After the Target

R.P. Duperray et al., Phys. Rev. D 68, 094017 (2003)

Fit to all available experimental results, especially at lower proton energies

K. Knie, [email protected], 4.12.2007

collecting pbars the magnetic horn
Collecting pbars:The Magnetic Horn

B  1/r

primary beam does not hit the horn

reaction products

K. Knie, [email protected], 4.12.2007

slide6

Collecting pbars:The Magnetic Horn

CERN ACOL Horn, I = 400 kA

K. Knie, [email protected], 4.12.2007

yield vs target length
Yield vs Target Length

target

target

p

pbar

sabs(p)

sprod(pbar)

sabs(pbar)

Absorption cross sections:

S.P. Denisov et al., Nucl. Phys. B 61, 62 (1973)

Production cross sections:

R.P. Duperray et al., Phys. Rev. D 68, 094017 (2003)

K. Knie, [email protected], 4.12.2007

yield vs target length1
Yield vs Target Length

target

target

p

pbar

sabs(p)

sprod(pbar)

sabs(pbar)

K. Knie, [email protected], 4.12.2007

yield vs target length2
Yield vs Target Length

target

p

pbar

sabs(p)

sprod(pbar)

sabs(pbar)

K. Knie, [email protected], 4.12.2007

yield vs target length3
Yield vs Target Length

target

p

pbar

sabs(p)

sprod(pbar)

sabs(pbar)

K. Knie, [email protected], 4.12.2007

slide11

MARS Simulation of the pbar Yields

pbars in the ellipse

yield =

primary protons

K. Knie, [email protected], 4.12.2007

slide12

MARS Simulation of the pbar Yields

p

pbar

Ir: sp = 1.8 bspbar=2.0 b

C: spbar=0.42 b

K. Knie, [email protected], 4.12.2007

slide13

Temperature Increase in the Target

cIr = 130 J kg-1 K-1

cCu = 385 J kg-1 K-1

cNi = 440 J kg-1 K-1

K. Knie, [email protected], 4.12.2007

slide15

Li Lens – A Possible Upgrade?

Lithium

sabs(pbar) = 176 mbarn

r(Li) = 0.535 g cm-3

l(lens) = 140 mm

T = 89 %

Copper

sabs(pbar) = 831 mbarn

r(Cu) = 8.96 g cm-3

l(lens) = 140 mm

T = 37 %

massive Li cylinder

B  r

primary beamgoes through the Li

reaction products

K. Knie, [email protected], 4.12.2007

slide16

Li Lens – A Possible Upgrade?

q < 100 mrad can be collected

I = 1 MA (I ~ r²)

Distance target center - lens: 100 mm

technically challenging / expensive

20 mrad < q < 80 mrad can be collected

I = 0.4 MA

Distance target center - lens: 220 mm

more simple and reliable, less expensive

K. Knie, [email protected], 4.12.2007

slide20

Li Lens – A Possible Upgrade?

Experimental data from CERN:A 34 mm/1.1 MA lens gave a 20% higher yieldcompared to a 0.4 MA horn:

K. Knie, [email protected], 4.12.2007

overall yield
Overall Yield

Yield → 240 p mm mrad, Dp/p = 3 %: 20 × 10-6 pbar/p

eSeparator 80 % 16 × 10-6pbar/p

eCR70 % 11 × 10-6pbar/p

eRESR70 % 8 × 10-6pbar/p

"The ... yields agree with the calculations except of an unexplained factor of 1.5" (Autin et al., EPAC 1990)5 × 10-6pbar/p (?)

exp. CERN (horn) 4.6× 10-6 pbar/p

CERN: design 50%

operation 63%→91%

2 × 1013 ppp, 0.1 Hz (1.0 - 1.6 ) × 107 pbar/sneeded for LHESR = 2× 1032cm-2s-12.0 × 107 pbar/s

K. Knie, [email protected], 4.12.2007

summary
Summary
  • Ni target: Less secondary particles, higher heat capacity compared to Ir or W:A Ni target can tolarate a 4 times higher beam intensity than an Ir target.
  • Smaller beamspot possible for Ni: Overcompensates the negative effect of Ni\'s lower density and therefore higher target length.
  • Simulations give a yield of 2 × 10-5 pbar/p (only target/horn):11 cm Ni target (d = 3 mm) in a graphite container, 0.62 mm (rms)beamspot. No target melting up to 4 × 1013 ppp. A dramatic improvement of this yield is not possible (without increasing the momentum acceptance of separator/CR).
  • This corresponds to an overall yield of 8 × 10-6 pbar/p (or somewhat below):eSepartor  80%, eCR  eRESR  70%
  • Simulations show no significant improvement with a Li lens instead of a horn:A Li lens\' collection efficiency is more sensitive to the target geometry. Ir target: at high beam intensities, the beamspot needs to be very large. Ni target: needs to be relatively long.
  • The repition rate is not limited by the target, but by the CR\'s cooling timeTime averaged, less than 1 kW beam power is deposited in the target at 0.1 Hz.

K. Knie, [email protected], 4.12.2007

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