| 1. |
|
|
| 2. |
- Schönhense, G., et al.
(författare)
-
Suppression of the vacuum space-charge effect in fs-photoemission by a retarding electrostatic front lens
- 2021
-
Ingår i: Review of Scientific Instruments. - : American Institute of Physics (AIP). - 0034-6748 .- 1089-7623. ; 92:5
-
Tidskriftsartikel (refereegranskat)abstract
- The performance of time-resolved photoemission experiments at fs-pulsed photon sources is ultimately limited by the e-e Coulomb interaction, downgrading energy and momentum resolution. Here, we present an approach to effectively suppress space-charge artifacts in momentum microscopes and photoemission microscopes. A retarding electrostatic field generated by a special objective lens repels slow electrons, retaining the k-image of the fast photoelectrons. The suppression of space-charge effects scales with the ratio of the photoelectron velocities of fast and slow electrons. Fields in the range from -20 to -1100 V/mm for E-kin = 100 eV to 4 keV direct secondaries and pump-induced slow electrons back to the sample surface. Ray tracing simulations reveal that this happens within the first 40 to 3 mu m above the sample surface for E-kin = 100 eV to 4 keV. An optimized front-lens design allows switching between the conventional accelerating and the new retarding mode. Time-resolved experiments at E-kin = 107 eV using fs extreme ultraviolet probe pulses from the free-electron laser FLASH reveal that the width of the Fermi edge increases by just 30 meV at an incident pump fluence of 22 mJ/cm(2) (retarding field -21 V/mm). For an accelerating field of +2 kV/mm and a pump fluence of only 5 mJ/cm(2), it increases by 0.5 eV (pump wavelength 1030 nm). At the given conditions, the suppression mode permits increasing the slow-electron yield by three to four orders of magnitude. The feasibility of the method at high energies is demonstrated without a pump beam at E-kin = 3830 eV using hard x rays from the storage ring PETRA III. The approach opens up a previously inaccessible regime of pump fluences for photoemission experiments.
|
|
| 3. |
|
|
| 4. |
|
|
| 5. |
|
|
| 6. |
|
|
| 7. |
|
|
| 8. |
- Wind, T., et al.
(författare)
-
An Inventory of Deceased Donor Family Care and Contact Between Donor Families and Recipients in 15 European Countries
- 2022
-
Ingår i: Transplant International. - : Frontiers Media SA. - 0934-0874 .- 1432-2277. ; 35
-
Tidskriftsartikel (refereegranskat)abstract
- Families of organ donors play an important role in the deceased organ donation process. The aim of this study was to gain insight into donor family care by creating an inventory of practice in various European countries. A questionnaire about donor family care and contact between donor families and recipients was developed. Representatives of the organ donor professionals of 15 European countries responded (94%). The donor coordinator plays a key role in care for the donor family. All countries provide information about the donation results to the families, although diminished due to privacy laws. Anonymous written contact between donor families and recipients is possible in almost all countries and direct contact in only a few. Remembrance ceremonies exist in most countries. Half of the respondents thought the aftercare could improve. This first inventory shows that differences exist between countries, depending on the organisation of the donation process, the law and the different role of the professionals. Direct contact between donor families and recipients is rarely supported by the donation organisation. To date there has been limited research about the experience of donor family aftercare and we would urge all donation organisations to consider this as a priority area.
|
|
