The transversely polarized target (PT) of the COMPASS (NA58) collaboration at CERN has been used for Drell–Yan measurements in 2015 and 2018. The transverse spin structure of the proton has been ...studied using a negative pion beam and a solid ammonia target. Employing the dynamic nuclear polarization (DNP) method, proton polarization values of more than 80% have been routinely achieved after one day, at a homogeneous magnetic field of 2.5 T and using a 3He/4He dilution refrigerator. During the data-taking the target operates in a transversely oriented magnetic dipole field at 0.6 T. This so-called frozen spin operation mode without the DNP pumping process leads to a slow depolarization of the target material, which is further accelerated by the heat input of the pion beam, produced secondary particles and radiation damage effects to the target material. Ammonia has the highest resistance against radiation-induced depolarization among known solid target materials. The proton polarization has been measured by the nuclear magnetic resonance (NMR). Relaxation times of about 1100 h have been observed for the proton polarization resulting in an average polarization between 68% and 76% during about two weeks long data-taking periods. To achieve a systematic uncertainty of the polarization ΔP/P as low as 3.2% and a statistical one of less than 1.8% two large target cells with appropriate positioning of the NMR-coils have been built.
We suggest using the Lagrange polynomial interpolation to calculate the longitudinal polarization of the large COMPASS target with a length of 2x55 cm. The algorithm does not change the polarizations ...measured by the NMR sensors. In addition, it allows taking into account the influence of the microwave field on the nuclear polarization at the resonator boundaries. As a result, measurements of polarization at several points of a long target and knowledge of the cavity design allow one to obtain a more explicit analytical expression for the target polarization. The work is performed in the COMPASS collaboration at CERN.
Target materials were exposed to a muon beam with an energy of 160GeV/c at the COMPASS experiment line in CERN-SPS to measure the production cross-sections for muon-induced radionuclides. A muon ...imager containing four nickel plates, each measuring 100mm×100mm, exposed to the IP plate successfully detected the muon beam image during an irradiation period of 33 days. The contrasting density rate of the nickel plate was (5.2±0.7)×10–9 PSL/muon per one-day exposure to IP. The image measured 122mm and 174mm in horizontal and vertical lengths, respectively, in relation to the surface of the base, indicating that 50±6% of the muon beam flux is confined to an area of 18% of the whole muon beam. The number of muons estimated from the PSL value in the total beam image area (0.81±0.1)×1013 was comparable to the total muon counts of the ion-chamber at the M2 beam line in the CERN-SPS. The production cross-sections of Cr-51, Mn-54, Co-56, Co-57, and Co-58 in nickel were 0.19±0.08, 0.34±0.06, 0.5±0.05, 3.44±0.07, 0.4±0.03 in the unit of mb, respectively, reducing muon associated particles effects. They are approximately 10 times smaller than that a proceeding study by Heisinger et al.
The COMPASS polarized target at CERN operates with irradiated ammonia (NH3) as a material having a reasonable content of polarizable nucleons and the highest resistance against radiation damages. We ...study the magnetic structure of ammonia polarized by the Dynamic Nuclear Polarization (DNP) method at 0.2K and 2.5T. In this material, electron spins, induced by ionizing radiation, couple proton and nitrogen nuclear spins by indirect J-interactions. This coupling and the dipole–dipole interactions between nuclear spins produce an asymmetry in the proton NMR line shape depending on the value of nitrogen polarization. We consider the asymmetry as an indirect imaging of the actual nitrogen spectra, useful for research developments and, in practice, for monitoring of nitrogen polarization in the long target, instead of a complicated analysis of NMR nitrogen spectra.
Deuterated polystyrene for polarized solid targets has been prepared by chemical doping with the trityl radical ‘Finland D36’ (AH 110 355 deutero acid form). Thin foils doped with various radical ...densities have been produced using tetrahydrofuran as solvent. Dynamic nuclear polarization technique has been applied to polarize deuterons in the samples (98%-D) at the temperature range of about 1K and magnetic fields of 2.5T and 5.0T. A maximum deuteron polarization of −61.5% with a build-up time of 100min has been achieved at 5.0T and about 500mK at a radical density of 1.16×1019spins/g.
•Deuterated polystyrene has been prepared by chemical doping with the trityl radical.•Thin foils doped with various radical densities have been produced.•Deuterons are polarized in the samples (98%-D) at about 1K and 2.5T and 5.0T.•Maximum D-polarization of −61.5% with a Tbu of 100min has been achieved.
A 2.5 m long liquid hydrogen target for COMPASS Bielert, E; Bremer, J; Doshita, N ...
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
05/2014, Letnik:
746
Journal Article
Recenzirano
Odprti dostop
A 2.5 m long liquid hydrogen target has been developed for the COMPASS experiment at CERN to investigate the nucleon spin structure via the Deeply Virtual Compton Scattering (DVCS) process. To ...recognize exclusive DVCS events, produced photons and slow protons need to be detected. In order to do so, the material budget around the target has to be minimal. A 0.125 mm thick Kapton super( registered )Kapton registered target cell and a 1 mm thick carbon fiber vacuum chamber with a Mylar super( registered )Mylar registered window have been constructed and tested. Finally, the target system was successfully employed during the DVCS pilot run in COMPASS at the end of 2012. The objective of this paper is to give a detailed description of this newly developed liquid hydrogen target apparatus.
A 2.5m long liquid hydrogen target for COMPASS Bielert, E.; Bremer, J.; Doshita, N. ...
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
05/2014, Letnik:
746
Journal Article
Recenzirano
Odprti dostop
A 2.5m long liquid hydrogen target has been developed for the COMPASS experiment at CERN to investigate the nucleon spin structure via the Deeply Virtual Compton Scattering (DVCS) process. To ...recognize exclusive DVCS events, produced photons and slow protons need to be detected. In order to do so, the material budget around the target has to be minimal. A 0.125mm thick Kapton® target cell and a 1mm thick carbon fiber vacuum chamber with a Mylar® window have been constructed and tested. Finally, the target system was successfully employed during the DVCS pilot run in COMPASS at the end of 2012. The objective of this paper is to give a detailed description of this newly developed liquid hydrogen target apparatus.
Performance of the COMPASS polarized target dilution refrigerator Doshita, N.; Ball, J.; Baum, G. ...
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
06/2004, Letnik:
526, Številka:
1
Journal Article
Recenzirano
The dynamic nuclear polarization (DNP) of
6
LiD
requires
1
mW/
g
or more microwave power in the beginning of the process. With the material of
350
g
, this gives more than
350
mW
in total for the ...COMPASS polarized target. A temperature around
300
mK
or below is needed for an efficient polarization. These low temperatures can only be achieved with a dilution refrigerator designed to operate with a
3
He
flow of
100
mmol/
s
. In order to keep the polarization in the frozen mode, temperatures of about
65
mK
are used with typical magnetic relaxation times of more than
1400
h
at
0.42
T
and of more than
15
000
h
at
2.5
T
. Low lattice temperature is important in achieving high nuclear polarization. The base temperature is limited by the heat brought to the mixing chamber by the inlet
3
He
and by radiation and conduction of heat.
Development of a polarized target for nuclear fusion experiments Iio, M.; Daito, I.; Doshita, N. ...
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
06/2004, Letnik:
526, Številka:
1
Journal Article
Recenzirano
A polarized deuterium target was developed for the use of the first measurement of the so-called complete spin dependent cross-sections of the
D
→
(
d
→
,p)T
nuclear reaction at
20
MeV
. In order to ...minimize the energy losses of incident and emitted particles in the target materials, the target thickness should be as thin as possible. A deuterated polyethylene foil of 30–
50
μm
thickness was used as polarized target. The deuterons contained in the foil are polarized by the dynamic nuclear polarization method in the magnetic field of
2.5
T
. The polarized deuterium target system has been installed in the 1st experimental hall of the Tandem Accelerator Center at the University of Tsukuba. From the target asymmetry measurement of
D
→
(d,d)D
elastic scattering by a
20
MeV
deuteron beam about 10% deuteron target polarization was confirmed.
PDF
