[en] Neon gas at pressures ranging from 0.8 to 6 torr is excited and ionized by means of microwave pulses of duration 2μs and with a repetition rate of 800Hz. Partial local thermodynamic equilibrium could not be found when studying neon line intensities. But when introducing helium as an impurity it was possible to determine an electron temperature from helium line intensities. A temperature Tsub(e)=2350+-250K is obtained during the microwave discharge and Tsub(e)=2400+-250K in the early afterglow (5μs). An interpretation is proposed for the variation of Tsub(e) with time in a Ne-He mixture

[en] Helium is excited by microwaves to set up a pulsed discharge at a pressure of a few torrs. Local partial thermodynamical equilibrium exists in the early afterglow. This fact is used to determine the electronic temperature, the value of which is 2800+-500K. During the first ten microseconds after the pulse it does not vary much. This result suggests that the gas temperature is 700+-100K

[en] Helium is excited by a pulsed microwave surfaguide at a pressure of a few Torr. A local partial thermodynamic equilibrium exists in the early afterglow-an equilibrium between the rotational levels of the He₂ molecules and another equilibrium between the high-lying atomic levels of helium (nsub(j) >= 4) and the electrons. Rotational temperature and an electronic temperature are thus deduced; rotational temperature is maximal near the wall (Tsub(r) is approximately equal to 700 +- 60 K) and the electronic temperature is spatially independent (Tsub(e) is approximately equal to 2500 +- 700 K). (author)

No abstract available

[en] Vibration-rotation interaction coefficients Fsub(vJ) were calculated for the e ³PIsub(g)- a ³Σsub(u)⁺ and E ¹PIsub(g)-A ¹Σsub(u)⁺ transitions of He₂ on the basis of a Morse-Pekeris potential and a polynomial expansion of the dipole-moment function M(r) Σsub(i)Msub(i)(r - rsub(e))sup(i) reduced to the first two terms. Owing to the importance of Fsub(vJ) they cannot be neglected when determining the rotational temperature of He₂ by spectroscopic methods involving line-intensity measurements. (author)

No abstract available

[en] This process and device for positron computed tomography imaging enhances time of flight method. The determination of gamma pair trajectory and disintegration position determines the memory position in which the event is recorded. This recording system avoids the use of reconstruction algorithms. It can build a high signal to noise ratio image with a simplified detection system (instead of costly detector rings), thus with a reduced cost detection system. (D.L.). 8 refs., 7 figs

[en] VOLUCAM is a new 3D Time Of Flight (TOF) Positron Emission Tomograph (PET) under investigation. As an aid to design this PET camera Monte Carlo simulation was developed to study its sensitivity performances. The simulation program is based on ITS 3.0, a general coupled electron-photon transport code that was adapted to obtain the results specific of PET design. The simulation follows each gamma ray, from creation in the phantom to detection in crystals or final escape by scoring every interaction, either in the phantom or in the crystals. (R.P.) 2 figs

[en] Recent progresses in fast time coincidence technique have permitted the use of time of flight (TOF) information in positron Emission Tomography. We describe the basic concept of positron time of flight imaging and introduce new concepts in order to incorporate the TOF data in the reconstruction process. An algorithm to recover positron activity is then proposed. We describe the image reconstruction in the TTVO1 time of flight camera, the system architecture and the special purpose operators. The time of flight tomography offers large development possibilities and we look forward the new high resolution, high signal-to-noise TOF camera

[en] A new generation of Time Of Flight (TOF) positron tomograph with high resolution and high count rate capabilities is under development in our group. After a short recall of the data acquisition process and image reconstruction in a TOF PET camera, we present the data acquisition system which achieves a data transfer rate of 0.8 mega events per second or more if necessary in list mode. We describe the reconstruction process based on a five stages pipe line architecture using home made processors. The expected performance with this architecture is a time reconstruction of six seconds per image (256x256 pixels) of one million events. This time could be reduce to 4 seconds. We conclude with the future developments of the system