| 1. |
- Albert, F, et al.
(författare)
-
Laser produced X-ray source in the 10-60 keV range at 1 kHz. Modified irradiation schemes in order to reach medical imaging quality
- 2001
-
Ingår i: Journal de Physique IV. - : EDP Sciences. - 1155-4339. ; 11:PR2, s. 429-432
-
Tidskriftsartikel (refereegranskat)abstract
- By tightly focusing ultra-short pulses from a Ti:sapphire terawatt laser onto a high-Z metallic target, hard x-ray pulses of short duration are produced. In most of our previous work concerning x-rays, a 150 mJ laser pulse with a 110 A duration has been used. Using mostly tin and tantalum targets, hard x-rays in the 10-60 keV range have been produced and used in differential absorption imaging around the K-alpha absorption edge of a contrast agent and also in imaging employing gated viewing for suppression of scattered radiation. In order to increase the x-ray yield (shortening the acquisition time) an increase in the laser repetition rate is desirable while still staying in the K-alpha energy regime. We have used a I kHz repetition-rate laser delivering 35 fs pulses in order to work towards these goals. We have clear evidence of hard x-ray generation above 30 keV, even for low laser pulse energies. We also studied the effect of a fs prepulse. The medical imaging capability of the source was explored. The use of a prepulse has been optimized in order to improve the image quality as well as the overall x-ray generation yield.
|
|
| 2. |
- Blagoev, K, et al.
(författare)
-
Radiative lifetimes of 6sns S-3(1) and 6snd D-3(1) excited states of HgI
- 2002
-
Ingår i: Physical Review A (Atomic, Molecular and Optical Physics). - 1050-2947. ; 66:3
-
Tidskriftsartikel (refereegranskat)abstract
- Natural radiative lifetimes have been measured along the 6sns S-3(1) (n=7-10) and 6snd D-3(1) (n=6-11) Rydberg series of neutral mercury using time-resolved laser-induced fluorescence spectroscopy in a laser-produced mercury plasma. The states of Hg I investigated in the present work were populated from the ground state by a stepwise excitation process. Relativistic Hartree-Fock calculations, including intravalence interactions and core-polarization effects, have been performed and the theoretical lifetimes have been compared with the measurements.
|
|
| 3. |
|
|
| 4. |
- Sjögren, Anders, et al.
(författare)
-
High-repetition-rate, hard x-ray radiation from a laser-produced plasma: Photon yield and application considerations
- 2003
-
Ingår i: Review of Scientific Instruments. - : AIP Publishing. - 1089-7623 .- 0034-6748. ; 74:4, s. 2300-2311
-
Tidskriftsartikel (refereegranskat)abstract
- We present an experimental study of hard x rays produced in laser-produced plasmas. The laser used is a 1 kHz system, delivering 0.7 mJ for 25 fs onto a solid target. The x-ray spectrum was measured with calibrated germanium detectors, allowing a very good estimate of the absolute number of photons emitted from the plasma over a wide energy range; from 7 keV to 0.5 MeV. Assuming a bi-Maxwellian electron distribution with temperatures of 4.5 and 63 keV, theoretical calculations support the experimental findings. The imaging characteristics of the x-ray source were investigated experimentally employing image plates and theoretically based on the electron distribution. (C) 2003 American Institute of Physics.
|
|
| 5. |
- Svanberg, Sune, et al.
(författare)
-
Generation, characterization, and medical utilization of laser-produced emission continua
- 2000
-
Ingår i: Laser and Particle Beams. - 0263-0346. ; 18:3, s. 563-570
-
Tidskriftsartikel (refereegranskat)abstract
- Intense continua of electromagnetic radiation of very brief duration are formed in the interaction of focused ultra-short terawatt laser pulses with matter. Two different kinds of experiments, which have been performed utilizing the Lund 10 Hz titanium-doped sapphire terawatt laser system are being described, where visible radiation and X-rays, respectively, have been generated. Focusing into water leads to the generation of a light continuum through self-phase modulation. The propagation of the light through tissue was studied addressing questions related to optical mammography and specific chromophore absorption. When terawatt laser pulses are focused onto a solid target with high nuclear charge Z, intense X-ray radiation of few ps duration and with energies exceeding hundreds of keV is emitted. Biomedical applications of this radiation are described, including differential absorption and gated-viewing imaging.
|
|
