Transcript Diapositiva 1 - Istituto Nazionale di Fisica Nucleare

High Density Jet Polarized Target
Molecular Polarization Workshop
Ferrara,Italy 16-18 June
Istituto Nazionale di Fisica Nucleare
Marco Capiluppi
A HIGH INTENSITY
COLD
SUPERCONDUCTING
JET POLARIZED
TARGET
Giuseppe Ciullo
Marco Contalbrigo
Paola Dalpiaz Ferretti
Paolo Lenisa
Michelle Stancari
Marco Statera
Ferrara University
How to increase the intensity of an
ABS?
2

B
pt
 increase the acceptance

2
m
 increase the input flow rate
Consequences
 Increased
beam attenuation
 lower magnet transmission?
 lower dissociation?
 pumping problems?
Why superconducting magnets?

2B pt
m
2
NIM A240 229 (1985)
 r
B  B pt 
 rpt




2
2 B pt
B
F  
  2 r
r
rpt
Calculated for cylindrical sextupoles using characteristics of NbTi wire
currently availible
FLOW RATE AT TARGET POINT
Qout
k
 2 Qin   f  t  1  A
4
k
number of selected states (1 or 2)

dissociation at nozzle exit
Qin input flux
f
fraction of atoms entering the first magnet
t
magnet transmission, calculated with ray-tracing code. Depends on vdrift and Tbeam
A
attenuation factor
NOVOSIBIRSK
HERMES
IUCF
FERRARA
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)
z(mm)
d(mm)
Bpt (T)
nozzle
0
2
skimmer
15
6.4-9.0
magnet 1
57-456
40 -100
6.0-1.2
magnet 2
756-1056
100-80
3.4-6.0
Target point
1250
20
Transmission t
 ray
tracing program (SCAN) that
calculates particle trajectories through the
magnetic field
 Based on code from CERN, expanded to
calculate beam densities and particle loss
distributions
Transmission t
Transmission t
Regeneration Time Estimate
 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
Q
time 
A
Est. Time = 72 hours
Rate of particle loss inside
chamber (atoms/sec)
Total cryogenic surface area
 A
A
FE
NOV
Q

Q
NOV
= 72 x (2-4) x 0.1
FE
=18-36 hours
ATTENUATION

Atoms of polarized jet collide with background
molecules (rest gas scattering)
 Atoms of polarized jet collide with each other
(intrabeam scattering)
number of
collisions per
unit volume
per unit time
d
rel
 
reln1n2
dVdt
Atomic jet
density
Density of
attenuating
particles
Interaction cross
section
Relative velocity of attenuating
particle 1 and jet atoms 2
d
number of collisions per unit volume per unit time
 rel n1n2
dVdt
p
rg
rest gas
rel  beam
n1 
  H1  H 2
kTrg
scattering
we can simpify this formula by assuming the densities are constant within the
transverse area
d
  n1n2   dz n1n2
Adtdz
dt
and observing that dN  
but
n1 
p rg
kTrg
normally used
formula
d
dz
d
  dz n1 An2
dz
we obtain
p rg
dN
  dz
N
kTrg
defining
N  An2
dN
  dz n1
N
dN   dz n1N
integrating, we have finally :
N ( z )  N 0e


kTrg
0 prg  d
z
intrabeam scattering: a tentative approach
z
n2 n1
z
DENSITY r-dependence
DENSITY z-dependence
d
number of collisions per unit volume per unit time
 
 rel n1n2
dVdt
intrabeam
scattering:
tentative
approach
rel   2  FWHM 
Density of
atoms at the
point r,,z
d
 n1n2
Adzdt
d
 n1n2 Adt
dz
d

  n1 N
dz
dz
beam
N ( z )  N 0e
  H1  H1
Density of
the jet
atoms at the
point r,,z
that will
arrive at the
target point
d
dN  
dz
dN

  n1
dz
N
beam


beam
z
0 n1
 d
ATTENUATION EVALUATION
N ib ( z )  N 0e

N rg ( z )  N 0e

beam

0 n1  d

kTrg
z
N ib ( z )
Sib 
e
N 0
0 prg  d
z
S rg 
1  A  SibSrg
HERMES attenuation
has been calculated as
the ratio beteween
the measured flowrate and a
theoretical flow-rate,
obtained from the
formula, using
SCAN for t,and n=1
for f, with A=0
Qout
N rg ( z )
N 0

e


z
beam

kTrg
0 n1  d
0 prg  d
z
k
 2 Qin   f  t  1  A
4
1  AHERMES
meas
Qout

Qth.
1  AHERMES  0.88 0.10
ATTENUATION ESTIMATES
/beam
fn1dz
Sib
Srg
(measured)
Sib Srg
Hermes
0.29
0.90x1018
0.88E0.06
0.91
0.80E0.07
Nov.
0.32
0.22x1018
0.97E0.06
IUCF
0.35
0.65x1018
0.89E0.06
Ferrara
0.32
1.03x1018
0.85E0.06
PRL 63 750 (1989)
PRA 46 6959 (1992)
}
(Koch thesis)
>0.95
0.92E0.10
(guess)
0.90
0.80E0.07
NIMA 336 410
>0.90
>0.70
 H1, H1   0.50  0.25 1018 m2
Ferrara Pumping System Requirements
Hermes
IUCF
Ferrara
S1 (l/s)
2x2200
2x2200
2x2200
Q1,jet (mbar l/s)
0.9900x1.5
0.9835x1.7
0.9484x3.0
P1(mbar)
1.2x10-4
3.4x10-4
<2.4x10-4
S2 (l/s)
2x1000
2x2200
2x2200
Q2,jet (mbar l/s)
0.0068x1.5
0.0280x1.7
0
p2 (mbar)
2.0x10-5
6.5x10-5
<1.0x10-5
p3 (mbar)
10-6 -10-7
10-6 -10-7
<10-7
Ferrara RGA
attenuation will be
no more than that
of Hermes and
IUCF
Comparison of measured and calculated intensities
Hermes
Nov.
IUCF
Ferrara
Qmeas(atoms/s)
Qth
6.8x1016
7.8x1016
6.7x1016
>58x1016
7.4x1016
8.1x1016
7.5x1016
73.1x1016
Qmeas/Qth
0.92E0.09
0.96E0.14
0.89E0.09
SibSrg
0.80E0.07
0.92E0.10
0.80E0.07
ttcelli
ttjet*
>0.70
(atoms/cm2)
0.9x1014
0.5x1014
0.9x1014
4.0x1014
djet=1 cm
0.3x1012
0.5x1012
0.3x1012
3.0x1012
djet=2 cm
0.7x1012
1.1x1012
1.2x1012
~10x1012
iAssuming HERMES cell geometry
*Assuming beam cross section P jet cross section
Qout
k
 2 Qin   f cos n   t vdrift, Tbeam   1  A
4
Hermes
Nov.
IUCF
Ferrara

0.80
0.90
0.75
0.65
Qin (mbar l/s)
1.5
3.8x1019
(molec/s)
0.6
1.7
3.0
1.5x1019 4.3x1019 7.5x1019
Bpt (T)
1.5
3.2
1.5
6.0
dmag (cm)
f
drift (m/s)
Tbeam (K)
dtp (cm)
t
0.86
1.4
1.04
4.0
0.0055
0.0134
0.0097
0.0211
1953
~1750
1494
1200
25.0
~30.0
16.5
15.0
1.0
2.0
1.0
2.0
0.45
0.44
0.24
0.35
THE SF-HELIUM CRYOSTAT
TOTAL HEAT LOAD = 4.6 W
He @2K CONSUMPTION < 5 l/h
SEXTUPOLE
MAGNET
THE COILS:
● NiTi wires
● 14X22 turns
COIL CROSS SECTION 19.2 X 19.5
2
mm
● Pole : steel with an iron core
● Height=232 mm outer diam.=109.1 mm
● R = 76.6 to 85.9 mm
c
TRAINING
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
550
500
450
Coil A
bobina
Coil B
bobina
I [A]
Coil C
bobina
Coil D
bobina
400
Coil E
bobina
Coil F
bobina
350
300
Quench
POLE TIP FIELD @ 4.2 K
MEASUREMENTS
DENSITY r-dependence
DENSITY z-dependence