A hydrogen-terminated diamond is a proven efficient electron emitter that can support emission of high average current. Several factors dictate the amplifier’s gain: the number of secondary electrons ...created at their point of entry into the diamond, the fraction of created electrons transmitted to the emitting face, and the fraction of transmitted electrons emitted. In this paper, we present a model detailing the impact of charge trapping at the surface on the instantaneous electric field inside the diamond, and its effect on the transmission gain. The ratio of instantaneous emitted electrons to the transmitted electrons depends on the electron’s energy distribution and the surface barrier. We calculated the latter by evaluating the magnitude of the negative-electron affinity that is modified by the Schottky effect due to the presence of the external applied field. The instantaneous values then were time integrated to yield the time-averaged ratio of the number of emitted electrons to the transmitted ones. The findings from the model agree very well with our experimental measurements. As an application of the model, we estimate the energy spread of the electrons inside the diamond from the measured secondary-electron emission.
Before starting reading Thracian Language and Greek and Thracian Epigraphy, we should keep in mind that we will be facing a situation that is extremely complex. There exists a methodological problem, ...originating in the past, which caused various misunders.
Structural and electrochemical characteristics of hypo–hyper d-electrocatalytic materials aimed for preparation of electrodes for hydrogen evolution were studied. The basic catalytic material was ...prepared of 10% amorphous Co (grain size <2
nm), 18% amorphous TiO
2 and Vulcan XC-72, by sol–gel procedure. A number of modifications were applied aimed at improving the materials performances: (i) TiO
2 was transformed into anatase by heating at 480
°C for 1
h, (ii) multiwalled carbon nanotubes (MWCNT) were used as a catalyst support instead of Vulcan XC-72 and (iii) Mo was added to Co phase in a quantity of 25
at.% (Mo:Co
=
1:3).
Both, material's intrinsic catalytic activity and surface area were affected by these modifications. As a result, the electrocatalytic activity for hydrogen evolution was improved, e.g. transformation of TiO
2 into anatase form lowers the HER overpotential (
η) for 15
mV at 60
mA
cm
−2. Introduction of MWCNTs lowered
η for 30
mV, while addition of Mo to metallic phase for 40
mV.
The complete modification of all three catalyst's components (10% MoCo
3
+
18% anatase
+
MWCNTs) was the most effective with 60
mV decrease of overpotential.
Characterization was made by XRD, SEM, IR and XPS methods. Surface area was measured by means of cyclic voltammetry.
Abstract
The LANSCE accelerator facility has been in operation for 50 years performing important scientific support for national security. The unique feature of the LANSCE accelerator facility is ...multi-beam operation, delivering beams to five experimental areas. To reduce long-term operational risks and to realize future beam performance goals in support of the laboratory missions, we are developing a novel high-brightness Front End injector. The proposed injector includes two independent low-energy transports for H
+
and H
-
beams merging beams at the entrance of a single RFQ. These beamlines also perform preliminary beam bunching before RFQ. The challenge of the present project is associated with the simultaneous acceleration of protons and H
-
ions with multiple beam flavors in a single RFQ, which has never been done before. The proposed injector must provide better than existing beam parameters while beam intensity is supposed to be increased by a factor of two and injection energy is reduced from 750 keV to 100 keV. The paper discusses the details of the design and presents injector parameters.
Structural and electrochemical characteristics of hypo–hyper d-electrocatalytic materials aimed for preparation of electrodes for hydrogen evolution were studied and modified in order to improve ...their performances. All studied materials were of general composition 10% Ni
+
18% TiO
2
+
C.
All materials were prepared of amorphous or crystalline TiO
2, crystalline Ni or NiCo (10–20
nm) and Vulcan XC-72, by sol–gel procedure.
Both, material's intrinsic catalytic activity and surface area were affected by applied modifications. As a result, the electrocatalytic activity was improved, e.g. transformation of TiO
2 into anatase form lowers the HER overpotential for 60
mV. Introduction of MWCNTs was even more effective, lowering
η for 120
mV. Co addition to metallic phase lowers
η for utmost 195
mV.
Combined modification of TiO
2 and carbon substrate lowers
η for 145
mV, while the complete modification of all three catalyst's components was the most effective with 230
mV decrease of overpotential.
PDF
