title: The Columbia University proton-induced soft x-ray microbeam.
abstract: A soft x-ray microbeam using proton-induced x-ray emission (PIXE) of characteristic titanium (K(α) 4.5 keV) as the x-ray source has been developed at the Radiological Research Accelerator Facility (RARAF) at Columbia University. The proton beam is focused to a 120 μm × 50 μm spot on the titanium target using an electrostatic quadrupole quadruplet previously used for the charged particle microbeam studies at RARAF. The proton induced x-rays from this spot project a 50 μm round x-ray generation spot into the vertical direction. The x-rays are focused to a spot size of 5 μm in diameter using a Fresnel zone plate. The x-rays have an attenuation length of (1/e length of ~145 μm) allowing more consistent dose delivery across the depth of a single cell layer and penetration into tissue samples than previous ultra soft x-ray systems. The irradiation end station is based on our previous design to allow quick comparison to charged particle experiments and for mixed irradiation experiments.
authors.affiliation: Center for Radiological Research, Columbia University, New York, NY 10032 USA.
authors.forename: Andrew D
authors.initials: AD
authors.lastname: Harken
authors.forename: Gerhard
authors.initials: G
authors.lastname: Randers-Pehrson
authors.forename: Gary W
authors.initials: GW
authors.lastname: Johnson
authors.forename: David J
authors.initials: DJ
authors.lastname: Brenner