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High Density Jet Polarized Target Molecular Polarization Workshop Ferrara,Italy 16-18 June.
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Transcript of High Density Jet Polarized Target Molecular Polarization Workshop Ferrara,Italy 16-18 June.
High Density Jet Polarized TargetHigh Density Jet Polarized Target
Molecular Polarization WorkshopMolecular Polarization Workshop
Ferrara,Italy 16-18 JuneFerrara,Italy 16-18 June
Marco Capiluppi
Giuseppe Ciullo
Marco Contalbrigo
Paola Dalpiaz Ferretti
Paolo Lenisa
Michelle Stancari
Marco Statera
Istituto Nazionale di Fisica Nucleare
Ferrara University
A HIGH INTENSITY COLD
SUPERCONDUCTING JET POLARIZED
TARGET
How to increase the intensity of an How to increase the intensity of an ABS?ABS?
increase the acceptanceincrease the acceptance increase the input flow rateincrease the input flow rate
Consequences
Increased beam attenuationIncreased beam attenuation lower magnet transmission?lower magnet transmission? lower dissociation?lower dissociation? pumping problems?pumping problems?
2
2
m
Bpt
2
2
m
Bpt
2
ptpt r
rBB
rr
B
r
BF
pt
pt2
2
Why superconducting magnets?
Calculated for cylindrical sextupoles using characteristics of NbTi wire currently availible
NIM A240 229 (1985)
FLOW RATE AT TARGET POINTFLOW RATE AT TARGET POINT
AtfQk
Q inout 124
kk number of selected states (1 or 2) number of selected states (1 or 2)
dissociation at nozzle exitdissociation at nozzle exit
QQinin input flux input flux
ff fraction of atoms entering the first magnet fraction of atoms entering the first magnet
tt magnet transmission, calculated with ray-tracing code. Depends on v magnet transmission, calculated with ray-tracing code. Depends on vdrift drift and Tand Tbeambeam
AA attenuation factor attenuation factor
NOVOSIBIRSK
HERMES
IUCF
FERRARA
z(mm)z(mm) d(mm)d(mm) BBptpt (T) (T)
nozzlenozzle 00 22
skimmerskimmer 1515 6.4-9.06.4-9.0
magnet 1magnet 1 57-45657-456 40 -10040 -100 6.0-1.26.0-1.2
magnet 2magnet 2 756-1056756-1056 100-80100-80 3.4-6.03.4-6.0
Target pointTarget point 12501250 2020
Ferrara Preliminary Design Parameters
Nozzle Temperature: 60 K Microwave Dissociator, y0.65 Input flux: 3.0 mbar l/s Superconducting magnets in superfluid He bath (1.8 K)
Transmission Transmission tt
ray tracing program (SCAN) that ray tracing program (SCAN) that calculates particle trajectories through the calculates particle trajectories through the magnetic fieldmagnetic field
Based on code from CERN, expanded to Based on code from CERN, expanded to calculate beam densities and particle loss calculate beam densities and particle loss distributions distributions
Transmission Transmission tt
Transmission Transmission tt
Est. Time = 72 hours QQ
AA
FE
NOV
NOV
FE = 72 x (2-4) x 0.1
=18-36 hours
A
Qtime
Cryogenic surfaces can adsorb 2-3 layers of molecules before saturating The magnet cryostat serves as a cryopump, and the chamber pressure is determined by the vapor pressure of H2 (~10-15 mbar at 2 K) until the surface begins to saturate
Rate of particle loss inside chamber (atoms/sec)
Total cryogenic surface area
Regeneration Time EstimateRegeneration Time Estimate
ATTENUATIONATTENUATION Atoms of polarized jet collide with background Atoms of polarized jet collide with background
moleculesmolecules ((rest gas scatteringrest gas scattering)) Atoms of polarized jet collide with each other Atoms of polarized jet collide with each other
(intrabeam scattering)(intrabeam scattering)
number of collisions per unit volume per unit time
Atomic jet density
Density of attenuating
particlesInteraction cross
sectionRelative velocity of attenuating
particle 1 and jet atoms 2
21nndVdt
drel
2nrel 1n
21nndVdt
drel
beamrel rg
rg
kT
pn 1
number of collisions per unit volume per unit timenumber of collisions per unit volume per unit time
rest gas scattering
21 HH
we can simpify this formula by assuming the densities are constant within the we can simpify this formula by assuming the densities are constant within the transverse area transverse area
21nnAdtdz
d
21nndt
dz21Anndz
dz
d defining 2AnN
and observing that dz
ddN
NndzdN 1we obtain
butrg
rg
kT
pn 1
1ndzN
dN
rg
rg
kT
pdz
N
dN
dpkTrg
zrg
eNzN
0
0)(
integrating, we have finally :
normally used formula
2n 1nz
z
intrabeam scattering: a tentative approach
DENSITY r-dependenceDENSITY r-dependence DENSITY z-dependenceDENSITY z-dependence
number of collisions per unit volume per unit timenumber of collisions per unit volume per unit time 21nndVdt
drel
intrabeam scattering: tentative approach
FWHMrel 2 11 HH
21nnAdzdt
d
Adtnndz
d21
dzNndz
d
beam
1dz
ddN
dznN
dN
beam
1
dnz
beameNzN
0 1
0)(
Density of the jet
atoms at the point r,,z that will
arrive at the target point
Density of atoms at the
point r,,z
rel
dn
ibib
z
beameN
zNS
0 1
0
)(
dpkTrg
rg
zrg
eNzN
0
0)(
ATTENUATION EVALUATIONATTENUATION EVALUATION
dpkTrgrg
rg
zrg
eN
zNS
0
0
)(
dn
ib
z
beameNzN
0 1
0)(
HERMES attenuation has been calculated as the ratio beteween the measured flow-rate and a theoretical flow-rate, obtained from the formula, using SCAN for t,and n=1 for f, with A=0
AtfQk
Q inout 124
.
1th
measout
HERMES Q
QA
rgibSSA1
10.088.01 HERMESA
beambeam ffnn11dd SSibib
SSrgrg
(measured)(measured)SSib ib SSrgrg
HermesHermes 0.290.29 0.90x100.90x101818 0.880.88EE0.060.06 0.910.91(Koch thesis)(Koch thesis)
0.800.80EE0.070.07
Nov.Nov. 0.320.32 0.22x100.22x101818 0.970.97EE0.060.06 >0.95>0.95(guess)(guess)
0.920.92EE0.100.10
IUCFIUCF 0.350.35 0.65x100.65x101818 0.890.89EE0.060.06 0.900.90NIMA NIMA 336336 410 410
0.800.80EE0.070.07
FerraraFerrara 0.320.32 1.03x101.03x101818 0.850.85EE0.060.06 >>0.900.90 >>0.700.70
ATTENUATION ESTIMATESATTENUATION ESTIMATES
21811 1025.050.0, mHH PRL 63 750 (1989)
PRA 46 6959 (1992)}
Ferrara Pumping System Requirements
HermesHermes IUCFIUCF FerraraFerrara
SS1 1 (l/s)(l/s) 2x22002x2200 2x22002x2200 2x22002x2200
QQ1,jet 1,jet (mbar l/s)(mbar l/s) 0.9900x1.50.9900x1.5 0.9835x1.70.9835x1.7 0.9484x3.00.9484x3.0
PP11(mbar)(mbar) 1.2x101.2x10-4-4 3.4x103.4x10-4-4 <2.4x10<2.4x10-4-4
SS2 2 (l/s)(l/s) 2x10002x1000 2x22002x2200 2x22002x2200
QQ2,jet 2,jet (mbar l/s)(mbar l/s) 0.0068x1.50.0068x1.5 0.0280x1.70.0280x1.7 00
pp2 2 (mbar)(mbar) 2.0x102.0x10-5-5 6.5x106.5x10-5-5 <1.0x10<1.0x10-5-5
pp3 3 (mbar)(mbar) 1010-6-6 -10 -10-7-7 1010-6-6 -10 -10-7-7 <10<10-7-7
Ferrara RGA attenuation will be no more than that
of Hermes and IUCF
HermesHermes Nov.Nov. IUCFIUCF FerraraFerrara
QQmeasmeas(atoms/s)(atoms/s) 6.8x106.8x101616 7.8x107.8x101616 6.7x106.7x101616 >58x10>58x101616
QQthth 7.4x107.4x101616 8.1x108.1x101616 7.5x107.5x101616 73.1x1073.1x101616
QQmeasmeas//QQthth 0.920.92EE0.090.09 0.960.96EE0.140.14 0.890.89EE0.090.09
SSibibSSrgrg 0.800.80EE0.070.07 0.920.92EE0.100.10 0.800.80EE0.070.07 >0.70>0.70
ttttcellcellii (atoms/cm(atoms/cm22)) 0.9x100.9x101414 0.5x100.5x101414 0.9x100.9x101414 4.0x104.0x101414
ttttjetjet** ddjetjet=1 cm=1 cm 0.3x100.3x101212 0.5x100.5x101212 0.3x100.3x101212 3.0x103.0x101212
ddjetjet=2 cm=2 cm 0.7x100.7x101212 1.1x101.1x101212 1.2x101.2x101212 ~10x10~10x101212
Comparison of measured and calculated intensities
iiAssuming HERMES cell geometry *Assuming beam cross section Assuming HERMES cell geometry *Assuming beam cross section PP jet cross section jet cross section
HermesHermes Nov.Nov. IUCFIUCF FerraraFerrara
0.800.80 0.900.90 0.750.75 0.650.65
QQin in (mbar l/s)(mbar l/s)
(molec/s)(molec/s)
1.51.5
3.8x103.8x101919
0.60.6
1.5x101.5x101919
1.71.7
4.3x104.3x101919
3.03.0
7.5x107.5x101919
BBpt pt (T)(T) 1.51.5 3.23.2 1.51.5 6.06.0
ddmag mag (cm)(cm) 0.860.86 1.41.4 1.041.04 4.04.0
ff 0.00550.0055 0.01340.0134 0.00970.0097 0.02110.0211
drift drift (m/s)(m/s) 19531953 ~~17501750 14941494 12001200
TTbeam beam (K)(K) 25.025.0 ~~30.030.0 16.516.5 15.015.0
ddtp tp (cm)(cm) 1.01.0 2.02.0 1.01.0 2.02.0
tt 0.450.45 0.440.44 0.240.24 0.350.35
ATvtfQk
Q beamdriftn
inout 1,cos24
THE SF-HELIUM CRYOSTAT
TOTAL HEAT LOAD = 4.6 WHe @2K CONSUMPTION < 5 l/h
THE COILS:● NiTi wires● 14X22 turns COIL CROSS SECTION 19.2 X 19.5 mm2
● Pole : steel with an iron core ● Height=232 mm outer diam.=109.1 mm ● R
c= 76.6 to 85.9 mm
SEXTUPOLE MAGNET
300
350
400
450
500
550
I [A
]
bobina A
bobina B
bobina C
bobina D
bobina E
bobina F
Coil
Coil
Coil
Coil
Coil
Coil
Quench
TRAINING
POLE TIP FIELD @ 4.2 K
coil 5 5 2 5 6 3 1 4 5 2 4 6
I [A] 357 456 452 492 490 494 496 500 515 518 513 517
MEASUREMENTS
DENSITY r-dependenceDENSITY r-dependence DENSITY z-dependenceDENSITY z-dependence