Report on WP1/M6: Report on low temperature measurements on superconductive
Al using an electron particle beam
M. Bassan4, D. Blair5, B. Buonuomo1, G. Cvallari1, E. Coccia3, S. D’Antonio2, G. Delle
Monache1, D. Di Gioacchino1, V. Fafone4, C. Ligi1, A. Marini1, G. Mazzitelli1, G.
Modestino1, G. Pizzella1, L. Quintieri1, S. Roccella1, A. Rocchi4, F. Ronga1, P. Tripodi1,
P. Valente6
INFN – Laboratori Naz. di Frascati, Frascati (RM) Italy
2
INFN – Sezione di Roma2, Roma Italy
3
INFN – Laboratori Naz. del Gran Sasso, Assergi (AQ) Italy
4
Dip. Di Fisica, Univ. di Roma Tor Vergata, Roma Italy
5
Physics, University of Western Australia, Nedlands Western Australia 6009
6
INFN – Sezione di Roma1, Roma Italy
1
Coordinator: G. Mazzitelli (INFN)
Two lines of activity were performed in the year: a) the commissioning of the dilution
refrigerator, needed to cool the AL5056 bar at temperatures below 1K where the material
is in the superconducting state and b) the completion of the analysis of the data taken
with the Niobium bar.
a) The manufacturer completed the shipment of the dilution refrigerator components on
January, 2006.
The assembly of the refrigerator inside the cryostat required the ex-novo realization of
parts and the first cooling at LHe temperature occurred on September, revealing leaks in
the cryogenic system. The completion of the commissioning is planned for Spring 2007.
b) The data collected in the year 2005 with the Nb bar have been fully analyzed and the
results have been published. A good agreement is found among observed and expected
values for Nb in normal state, as shown in Table. For Nb in superconducting state a
linear dependence of Xmeas on the measured energy deposited by the beam pulses in the
bar is found (see figure).
T[K]
m
m
275 0.96 0.01
81
1.03 0.01
12.5 0.95 0.01
Values of m fitting Xmeas = m * Xexp and error m
Nb,T = 4.5K. Correlation between measured first longitudinal mode of oscillation
(FLMO) maximum amplitudes Xmeas and energy (W), deposited by beam pulses in the
bar, as derived by Ne measurements
Next figure (left) shows the measured FLMO maximum amplitudes normalized to W
above and below Tc, together with the expectations computed using the first mode of
comparison
B0n for T>Tc and B0super for T<Tc. The quantity Xmeas-B0n(1+) is checked against Xtr, as
given by:
Xexp=Xtr+Xn= (2WL)/(3 M)((V/V)/(H/V))+B0n
for assessing the second mode of comparison (right), which seems to explain better the
data in the region 4 K<T<8 K.
Nb - Left: FLMO maximum amplitudes (X) normalized to the total energy lost per beam
pulse (W) vs. temperature (T). Circles: measured values. Bands: expected values. Right:
The component of the FLMO maximum amplitude due to local transitions normalized to
the energy lost (Xtr/W) vs. temperature (T). Circles: observed values. The region enclosed
by the broken lines shows the expected values.
The expected rate of cosmic ray coincidences in NAUTILUS was evaluated by using
B0n=(2nLW)/( cVnM)
in normal state.
The results obtained by RAP with the Nb bar suggest that the amplitude of oscillations
due to the energy released by particles impinging on the bar depends on the state of
conduction. While for niobium in the superconducting state the FLMO maximum
amplitude is observed and expected smaller than in the normal state, the contrary
is expected for aluminum. However, a final confirmation will be obtained by performing
the measurements with the AL5056 bar cooled at temperatures below 1K.