An electron collimator composed of a point-like source and a parabolic pn junction is proposed as a generator of highly focused electron beams in graphene. The collimator is based on negative refraction and Klein collimation, which are unique to pseudo-relativistic Dirac materials. The electron beams generated by the lensing apparatus can be steered by a weak magnetic field without losing colli...

background: obtaining high quality images in single photon emission tomography (spect) device  is the most important goal in nuclear medicine. because if image quality is low, the possibility of making a mistake in diagnosing and treating the patient will rise. studying effective factors in spatial resolution of imaging systems is thus deemed to be vital. one of the most important factors in sp...

Introduction: The Monte Carlo simulation is used to enhance reliability in the experiments related to nuclear instruments. in addition, that is used to calculate the different components of the neutron and gamma ray fluxes in boron neutron capture therapy(BNCT) and neutron capture (NCT)applications. BNCT is one of the methods in radiotherapy, that is used the neutron beam for ki...

Tantalum-178 is a short-lived radionuclide (Tm = 9.3 min.) and emits primarily 56to 64-keV characteristic x-rays. We have determined the imaging characteristics with this radionuclide and a large-field-of-view Anger camera. With a pinhole collimator, good spatial resolution is possible with Ta-178, although the image quality is superior with Tc-99m under comparable conditions. Spatial resolutio...

We analyzed the physical basics for design of absorbers for high energy beams of electrons and photons. Typical examples are the collimators and dump systems. In particular, we considered a collimator for usage in Cornell ERL project, where it could be used for reduction of γ , − e halo, minimization of exposure SRF module to SR from neighboring bending magnet and for absorption of direct beam ...

The American Association of Physicists in Medicine Task Group 36 (AAPM TG-36) data can be used to estimate peripheral dose (PD) distributions outside the primary radiation field. However, the report data does not apply to linear accelerators equipped with a multileaf collimator (MLC) and universal wedge (UW). Tertiary multileaf collimators have been shown to significantly affect PD distribution...

An important method in cancer treatment is the use of high energetic radiation. In order to kill tumor cells the patient is exposed to radiation that is delivered by a linear accelerator whose beam head can be rotated about the treatment couch. Inevitably the healthy tissue surrounding the tumor is also exposed to some radiation. So the problem arises to arrange the treatment in a way such that...

Tantalum-178 is a short-liver radionuclide (T 1/2 = 9.3 min.) and emits primarily 56- to 64-keV characteristic x-rays. We have determined the imaging characteristics with this radionuclide and a large-field-of-view Anger camera. With a pinhole collimator, good spatial resolution is possible with Ta-178, although the image quality is superior with Tc-99m under comparable conditions. Spatial reso...