Experimental energy resolution of a paracentric hemispherical deflector analyzer for different entry positions and bias

Abstract

A specially designed hemispherical deflector analyzer (HDA) with 5-element input lens having a movable entry position R0 suitable for electron energy analysis in atomic collisions was constructed and tested. The energy resolution of the HDA was experimentally determined for three different entry positions R0 = 84, 100, 112 mm as a function of the nominal entry potential V(R0) under pre-retardation conditions. The resolution for the (conventional) entry at the mean radius R0 = 100 mm was found to be a factor of 1.6-2 times worse than the resolution for the two (paracentric) positions R0 = 84 and 112 mm at particular values of V(R0). These results provide the first experimental verification and a proof of principle of the utility of such a paracentric HDA, while demonstrating its advantages over the conventional HDA: greater dispersion with reduced angular aberrations resulting in better energy resolution without the use of any additional fringing field correction electrodes. Supporting simulations of the entire lens plus HDA spectrometer are also provided and mostly found to be within 20%-30% of experimental values. The paracentric HDA is expected to provide a lower cost and∕or more compact alternative to the conventional HDA particularly useful in modern applications utilizing a position sensitive detector.

Experimental energy resolution of a paracentric hemispherical deflector analyzer for different entry positions and bias simulated in SIMION

“…These results are shown in Fig:4 as the dotted green line. With the exception of the cases of R 0 = 84 mm with γ >1.5 good overall consistency was found [5] between the two approaches which usually differed by less than ∼15% for most points evaluated. The resolution for the (conventional) entry at the mean radius R 0 = 100 mm was found to be a factor of 1.6-2 times worse than the resolution for the two (paracentric) positions R 0 = 84 and 112 mm at particular values of the bias V(R 0 ).…”

Zero-degree Auger Projectile Electron Spectroscopy of Li-like Ions obtained in Collisions of 1s2s 3S He-like Ions with Gaseous Targets

“…With this system a stable analyser chamber vacuum of ∼ 10 −6 Torr can be maintained for typical gas cell pressures in the mTorr range. The Auger electrons emitted at zero degrees with respect to the beam direction are analysed in energy with a maximum resolution ∆E E ∼0.1% using an electrostatic paracentric [31][32][33][34][35] hemispherical deflector analyser (HDA) equipped with a 4-element focusing/deceleration entry lens and a 2-dimensional position sensitive detector (PSD) 36,37 . Since the energy resolution is fixed by the spatial characteristics of the analyser, higher absolute resolution ∆E is achieved by pre-retarding http://epublishing.ekt.gr | e-Publisher: EKT | Downloaded at 03/07/2020 18:27:17 | 18%, (4) foil(P) -gas(T) = 19%, (5) gas(P) -foil(T) = 24%, (6) gas(P) -gas(T) = 25%.…”

Electrostatic afocal-zoom lens design using computer optimization technique

“…This type of lens has been utilized in electron spectrometers [35,36], although the details of the lens design and performance have not been reported. There is also a lack of data in the literature for a wide range of (M, V 5 /V 1 ) sets.…”