We demonstrate a stationary helium gas density gradient which is needed for a proposed novel low-energy μ+ beam line. In a closed system with constant pressure the corresponding density gradient is ...only a function of the temperature. In a neutron radiography experiment two gas cells with different geometries were filled with 3He gas at constant pressures of about 10mbar. Temperatures in the range from 6K to 40K were applied and density distributions with a maximum to minimum density ratio of larger than 3 were realized. The distribution was investigated employing the strongly neutron absorbing isotope 3He. A simple one-dimensional approach derived from Fourier׳s law describes the obtained gas density with a deviation <2%.
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Here is a short paper on precision physcis experiments at low energies. Such experiments use methods of nuclear, particle and atomic physics providing some of the most sensitive tests of our ...present best theories of nature. Hoping that this is most accessible, I have chosen an illustrative approach, giving 6 examples of such experiments with neutrons and muons addressing various aspects of the known fundamental interactions and open issues. The list of references puts emphasis for some examples more on the historic, original publications, for others on the latest results and sometimes just refers to review articles. It is not aiming at the most comprehensive picture but at attracting the reader’s interest and providing starting points for further studies.
The PSI ultra-cold neutron source Anghel, A.; Atchison, F.; Blau, B. ...
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
12/2009, Letnik:
611, Številka:
2
Journal Article
Recenzirano
A new type of ultra-cold neutron (UCN) source based on the spallation process is under construction at PSI. The essential elements are a pulsed proton beam with highest intensity (
I
p
≥
2
mA
) and a ...low duty cycle (1%), a lead spallation target, a large
D
2
O
moderator and a solid deuterium (
sD
2
) converter system. Spallation neutrons are thermalized in the
D
2
O
, further cooled and partially downscattered into the ultra-cold neutron range in the
sD
2
. The expected UCN density is higher than
1000
UCN
/
cm
3
in typical experiments, an increase of almost two orders of magnitude over the best source currently available (at ILL). The new UCN source is expected to come into operation in 2009.
We have measured the transmission of ultra-cold neutrons (UCN) through tubes coated on the inside with materials of high optical potentials. The best transmission value, T, normalised to 1m long UCN ...guides was obtained with a beryllium coated quartz guide, T=(99.0±1.0)%. Furthermore, excellent transmission coefficients were found for (i) a glass tube coated with NiMo(88/12), T=(97.3 ±0.6)%, (ii) a NiMo(85/15) guide made by the replication technique, T=(97.1 ±0.8)% and (iii) a glass guide coated with NiMo(82/18), T=(96.3 ±2.1)%. The results demonstrate that UCN guides made from coated glass tubes have the same excellent transmission properties as those produced with the replication technique. They are, however, significantly cheaper.
Muonic atoms have been used to extract the most accurate nuclear charge radii based on the detection of X-rays from the muonic cascades. Most stable and a few unstable isotopes have been investigated ...with muonic atom spectroscopy techniques. A new research project recently started at the Paul Scherrer Institut aims to extend the highresolution muonic atom spectroscopy for the precise determination of nuclear charge radii and other nuclear structure properties of radioactive isotopes. The challenge to combine the high-energy muon beam with small quantity of stopping mass is being addressed by developing the concept of stopping the muon in a high-density, a high-pressure hydrogen cell and subsequent transfer of the muon to the element of interest. Status and perspectives of the project will be presented.
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