Ult
Ultracold
ld N
Neutron
t
IInstrumentation
t
t ti
Marie Blatnik; Albert Young: For the UCNB Collaboration
L Al
Los
Alamos N
National
ti
l Lab
L
Lab,
b Andy
A dy Saunders
S
d
D t off Electrical
Dept
El t i l and
d Computer
C
t E
Engineering
Engineering,
i
i
W
Washkewicz
hk i C
College
ll
off E
Engineering
i
i
Cleveland State University
MOTIVATION
POLARIMETRY
DETECTION
Figure
g
10: Below,,
photograph of a
preamplifier
lifi bboard,
d
with 6 channels,
with the FET in
liquid
q
nitrogen.
g
A silver-plated
p
8-rungg birdcage
g resonator was chosen for the spin-flipping
p
pp g design
g as a
compromise between zeroth
zeroth-mode
mode uniformity and decreased Q due to resistance.
resistance
End
d
Drive
Figure 11: Feynman
Fi
F
diagram
d
g
of
o neutron
eu o beta
be
decay;
Rung
g
Drive
n → p + e + ve
no inter-nucleon
inter nucleon forces
i
f with
i h the
h ddecay.
interfere
Figure
g
4: AFP spin-flipper.
pi flipp
This birdcage resonator
produces a resonant
sinusoidal standing
g wave
for neutron flips
flips.
Left: Two driving methods
methods.
Right: End-driven
End driven with a
ppick-upp coil inside of the
standing wave
wave.
Each rung’s
rung s impedance Zi = 1/(jωCi) + jωLi can be adjusted by tuning the self-inductance
self inductance
rung, which
hi h adjusts
dj t the
th resonantt frequency
f
f = 1/(2
1/(2π√LC).
√LC)
PROBLEM DEFINITION
Constraints on the resonator are specified by the AFP magnet. The field is measured and
t
tweaked,
k d with
ith the
th peakk resonantt condition
diti chosen
h
as bbetween
t
B = 00.977
977 T andd 0.972
0 972 T.
T
Experiment Requirements:
Shim Coil Cycle Field Evolution
SPICE simulations of the preamplifier help tune the component values to maximize SNR
and minimize rise time
time. Cd-109,
Cd 109 Bi-207,
Bi 207 and Ce-139
Ce 139 were used to characterize the pixels
pixels.
Simulated Preamp Transient
Response
R
Ma
agn
netic Fiel
F d [T
T]
1. Well-characterized and efficient neutron ppolarization ((+ and -).
)
Fit and Measured Field Profiles
for Various Silicon Capacitance
Bore Position [mm]
[
]
The spin-flipping
spin flipping region of the magnet requires a
radiofrequency
q
y birdcage
g resonator,, which produces
p
a field
that slowly rotates in the neutron
neutron’ss reference frame tuned to:
ωrot = B·29.2
B 29.2 MHz/T.
N d Hi
Needs:
High
hU
Uniformity
if
it and
d Hi
High
hQ
Q.
2.
2 Efficient detection of decay products.
products
Figure 5: The field profile is monotonically
decreasing for the field corresponding to the spin
spinflipper
pp frequency
q
y ((red line),
), but not acceptable
p
within the 0.15
0 15 MHz variation band (pink lines).
lines)
Frequency Tuning for Various Drive
Modes
32
31
30
29
28
27
26
D ||
Dec ||
Cou ||
Cou ||
Dec Ser
Cou Ser
Desire: 28.5 MHz
Set X: 8.7453 cm
6
8
10
Ri Di
Ring
Displacement
l
t [cm]
[ ]
Nd
N-doped
d Sili
Silicon
~> 15
15.22 ns
Figure 6: Each shim coil response was
individually mapped as a basis for a
superposition
p p
calculation to fit a slow 0.4 G/cm The cadmium spectrum suggests that the protons will resolve in the silicon,
silicon and the noise
gradient
gradient.
i characterized
is
h
t i d iin th
the ffollowing
ll i pixel
i l map.
The inductance ring is tuned using a spectrum analyzer,
analyzer and the Q is measured.
measured
R ona
Reso
ant freq
f quencyy [M
MHzz]
Figure
g
2: Diagram
g
of the AFP magnet.
g
Spin
p manipulation
p
is
performed with this magnet,
magnet which contains one main coil for the
polarizing
l i i fi
field
ld (7 T) andd the
th spin-flipping
i fli i fi
field
ld ((~1
1 T)
T), and
d 10
smaller “shim” coils to smooth out the field profile.
p
Figure 11: Detector
response peak: 65.6
65 6
MH
MHz
•1 pF = 16. ns
•10 pF = 18. ns
•20
20 pF
F = 20
20. ns
•30
30 pF = 22
22.74
74 ns
•40 pF = 25
25.235
235 ns
Figure
g
7: The
resonator can be
rung driven ( || )
rung-driven
or end-driven ((ser),
),
and measured by
a pick-up
pick p coil
((dec)) or byy
absorption (cou)
(cou).
Figure
g
8:
Frequency
response of the
resonator from
a network
anal er
analyzer.
Cadmium 109
Resonator Frequency Response (dB)
Q = fc/Δf
f /Δf = 330
Figure 12: Noise characterization
Conclusions and Future Work
Conclusions and Future Work
P-doped
P
doped Silicon
Needs:
d
Figure 3: Diagram of a silicon detector. The incoming radiation
disturbs the depletion region of the reverse
reverse-biased
biased silicon,
silicon
creating
i a small
ll current off electrons
l
and
d hholes.
l
Electrons reflect;
El
fl ; timing
i i g must bbe on the
h order
d off 10 ns.
Protons have very little velocity; they will be accelerated to
30 keV. The SNR must be maximized to see them.
• T
Troubleshoot
bl h t ttrigger,
i
noise,
i th
thresholds
h ld tto see protons.
t
• Regang the channels for a physics run.
run
• Better
B tt shielding
hi ldi g and
d DAQ
Q filt
filtering
i g to
t escape
p oscillations.
ill ti
D
December
b 2014 D
Data R
Run:
J F b 2015 Data
Jan-Feb
D Run:
R
• Poor neutron flux
flux.
• Neutron
N t
leakage.
l k
• Poor vacuum.
• Imperfect but acceptable stability.
stability
• Beta particles detected.
B t
ti l d t t d
• Protons mysteriously absent.
Acknowledgments
Fi
Figure
13 The
13:
Th pixels
i l will
ill bbe evenly
l gangedd to
t distribute
di t ib t silicon
ili
capacitance.
it
JJ. Bacon, A. Brandt, L. J. Broussard, C. Cude, E.B. Dees, A.T. Holley, T. Ito, M. Makela, P. McGaughey, J. Mirabal, Bacon A Brandt L J Broussard C Cude E B Dees A T Holley T Ito M Makela P McGaughey J Mirabal
C Morris R Neise R W Pattie J Ramsey D J Salvat S Sjue A Sprow T Womack B Zeck
C. Morris, R. Neise, R. W. Pattie, J. Ramsey, D.J. Salvat, S. Sjue, A. Sprow, T. Womack, B. Zeck