0000000000430603
AUTHOR
P. Scholz
showing 6 related works from this author
Major results from the first plasma campaign of the Wendelstein 7-X stellarator
2017
After completing the main construction phase of Wendelstein 7-X (W7-X) and successfully commissioning the device, first plasma operation started at the end of 2015. Integral commissioning of plasma start-up and operation using electron cyclotron resonance heating (ECRH) and an extensive set of plasma diagnostics have been completed, allowing initial physics studies during the first operational campaign. Both in helium and hydrogen, plasma breakdown was easily achieved. Gaining experience with plasma vessel conditioning, discharge lengths could be extended gradually. Eventually, discharges lasted up to 6 s, reaching an injected energy of 4 MJ, which is twice the limit originally agreed for t…
Precise determination of the 1s Lamb Shift in hydrogen-like heavy ions at the ESR storage ring using microcalorimeters
2015
The precise determination of the energy of the Lyman α1 and α2 lines in hydrogen-like heavy ions provides a sensitive test of quantum electrodynamics in very strong Coulomb fields. To improve the precision of such experiments, the new detector concept of microcalorimeters, which detect the temperature change of an absorber after an incoming particle or photon has deposited its energy as heat, is now exploited. The microcalorimeters for x-rays used in these experiments consist of arrays of silicon thermometers and x-ray absorbers made of high-Z material. With such detectors, a relative energy resolution of about 1 per mille is obtained in the energy regime of 50–100 keV. Two successful measu…
Overview of first Wendelstein 7-X high-performance operation
2019
Abstract The optimized superconducting stellarator device Wendelstein 7-X (with major radius , minor radius , and plasma volume) restarted operation after the assembly of a graphite heat shield and 10 inertially cooled island divertor modules. This paper reports on the results from the first high-performance plasma operation. Glow discharge conditioning and ECRH conditioning discharges in helium turned out to be important for density and edge radiation control. Plasma densities of with central electron temperatures were routinely achieved with hydrogen gas fueling, frequently terminated by a radiative collapse. In a first stage, plasma densities up to were reached with hydrogen pellet injec…
High-precision X-ray spectroscopy of highly-charged ions at the experimental storage ring using silicon microcalorimeters
2017
Abstract X-ray spectroscopy on highly charged heavy ions provides a sensitive test of quantum electrodynamics in very strong Coulomb fields. One limitation of the current accuracy of such experiments is the energy resolution of available X-ray detectors for energies up to 100 keV. To improve this accuracy, a novel detector concept, namely the concept of microcalorimeters, is exploited for this kind of measurements. The microcalorimeters used in the present experiments consist of silicon thermometers, ensuring a high dynamic range, and of absorbers made of high-Z material to provide high X-ray absorption efficiency. Recently, besides an earlier used detector, a new compact detector design, h…
Isotopic distributions of thermal-neutron-induced fission fragments of near-symmetric fission of Pu239,241 determined using calorimetric low-temperat…
2021
Isotopic distributions were measured for the light fragment group in the transition region from asymmetric to symmetric fission for thermal neutron induced fission of $^{239}\mathrm{Pu}$ and $^{241}\mathrm{Pu}$ using the novel technology of calorimetric low temperature detectors in combination with the passive absorber method. Nuclear charge distributions were determined for 24 masses in the range $A=89$ to $A=112$ for $^{241}\mathrm{Pu}({n}_{\mathrm{th}},f)$ for the first time with the LOHENGRIN mass spectrometer. Moving from asymmetric to symmetric fission, known data were supplemented for masses from $A=110$ to $A=112$ for $^{241}\mathrm{Pu}({n}_{\mathrm{th}},f)$ and from $A=109$ to $A=1…
Precise determination of the 1s Lamb shift in hydrogen-like lead and gold using microcalorimeters
2016
Quantum electrodynamics in very strong Coulomb fields is one scope which has not yet been tested experimentally with suffcient accuracy to really determine whether the perturbative approach is valid. One sensitive test is the determination of the 1s Lamb Shift in highly-charged very heavy ions. The 1s Lamb Shift of hydrogen-like lead (Pb81+) and gold (Au78+) has been determined using the novel detector concept of silicon microcalorimeters for the detection of hard X-rays. The results of (260 +- 22) eV for lead and (208 +- 13) eV for gold are within error bars in good agreement with theoretical predictions. For hydrogen-like lead, this represents the most accurate determination of the 1s Lam…