12 research outputs found
SDR, EVC, and SDREVC: Limitations and Extensions
Methods for reducing the radius, temperature, and space charge of nonneutral
plasma are usually reported for conditions which approximate an ideal Penning
Malmberg trap. Here we show that (1) similar methods are still effective under
surprisingly adverse circumstances: we perform SDR and SDREVC in a strong
magnetic mirror field using only 3 out of 4 rotating wall petals. In addition,
we demonstrate (2) an alternative to SDREVC, using e-kick instead of EVC and
(3) an upper limit for how much plasma can be cooled to T < 20 K using EVC.
This limit depends on the space charge, not on the number of particles or the
plasma density.Comment: Version 2: a small discrepancy between the N values for Table 1 and
Fig. 3 led to an investigation of the charge counting diagnostic. There is a
small energy dependence which only became apparent following improvements to
pre-SDREVC. The pulsed dump was modified to reduce this dependence. The data
for Table 1 and Fig. 3 was taken again with the improved method
Slow positron production and storage for the ASACUSA-Cusp experiment
The ASACUSA (atomic spectroscopy and collisions using slow antiprotons) Cusp experiment requires the production of dense positron plasmas with a high repetition rate to produce a beam of antihydrogen. In this work, details of the positron production apparatus used for the first observation of the antihydrogen beam, and subsequent measurements, are described in detail. This apparatus replaced the previous compact trap design resulting in an improvement in the positron accumulation rate by a factor of 52 +/- 3
SDR, EVC, and SDREVC: Limitations and Extensions
Methods for reducing the radius, temperature and space charge of a non-neutral plasma are usually reported for conditions which approximate an ideal Penning Malmberg trap. Here, we show that (i) similar methods are still effective under surprisingly adverse circumstances: we perform strong drive regime (SDR) compression and SDREVC in a strong magnetic mirror field using only 3 out of 4 rotating wall petals. In addition, we demonstrate (ii) an alternative to SDREVC, using e-kick instead of evaporative cooling (EVC) and (iii) an upper limit for how much plasma can be cooled to T < 20 K using EVC. This limit depends on the space charge, not on the number of particles or the plasma density
Upgrade of the positron system of the ASACUSA-Cusp experiment
The ASACUSA-Cusp collaboration has recently upgraded the positron system to
improve the production of antihydrogen. Previously, the experiment suffered
from contamination of the vacuum in the antihydrogen production trap due to the
transfer of positrons from the high pressure region of a buffer gas trap. This
contamination reduced the lifetime of antiprotons. By adding a new positron
accumulator and therefore decreasing the number of transfer cycles, the
contamination of the vacuum has been reduced. Further to this, a new rare gas
moderator and buffer gas trap, previously used at the Aarhus University, were
installed. Measurements from Aarhus suggested that the number of positrons
could be increased by a factor of four in comparison to the old system used at
CERN. This would mean a reduction of the time needed for accumulating a
sufficient number of positrons (of the order of a few million) for an
antihydrogen production cycle. Initial tests have shown that the new system
yields a comparable number of positrons to the old system.Comment: 10 pages, 5 figures, under consideration for the Special Collection
"Non-Neutral Plasmas: Achievements and Perspectives" in JP
Slow positron production and storage for the ASACUSA-Cusp experiment
The ASACUSA Cusp experiment requires the production of dense positron plasmas
with a high repetition rate to produce a beam of antihydrogen. In this work,
details of the positron production apparatus used for the first observation of
the antihydrogen beam, and subsequent measurements are described in detail.
This apparatus replaced the previous compact trap design resulting in an
improvement in positron accumulation by a factor of (Comment: 9 pages, 7 figure