Effective temperature of an ultracold electron source based on near-threshold photoionization

We present a detailed description of measurements of the effective temperature of a pulsed electron source, based on near-threshold photoionization of laser-cooled atoms. The temperature is determined by electron beam waist scans, source size measurements with ion beams, and analysis with an accurate beam line model. Experimental data is presented for the source temperature as a function of the wavelength of the photoionization laser, for both nanosecond and femtosecond ionization pulses. For the nanosecond laser, temperatures as low as 14±3 K were found; for femtosecond photoionization, 30±5 K is possible. With a typical source size of 25 um , this results in electron bunches with a relative transverse coherence length in the 10-4 range and an emittance of a few nm rad

Sigma-1 Agonist Binding in the Aging Rat Brain: a MicroPET Study with [11C]SA4503

Purpose: Sigma-1 receptor ligands modulate the release of several neurotransmitters and intracellular calcium signaling. We examined the binding of a radiolabeled sigma-1 agonist in the aging rat brain with positron emission tomography (PET). Procedures: Time-dependent uptake of [11C]SA4503 was measured in the brain of young (1.5 to 3 months) and aged (18 to 32 months) Wistar Hannover rats, and tracer-kinetic models were fitted to this data, using metabolite-corrected plasma radioactivity as input function. Results: In aged animals, the injected probe was less rapidly metabolized and cleared. Logan graphical analysis and a 2-tissue compartment model (2-TCM) fit indicated changes of total distribution volume (VT) and binding potential (BPND) of the tracer. BPND was reduced particularly in the (hypo)thalamus, pons, and medulla. Conclusions: Some areas showed reductions of ligand binding with aging whereas binding in other areas (cortex) was not significantly affected. © 2015 The Author(s