Katsuyuki Kinoshita

Femtosecond streak tube

A new design concept of a streak tube is conceived to obtain femtosecond temporal resolution. It is based on four factors as follows. First, in order to decrease the photoelectron transit time spread, one must investigate how high electric field is practically usable near the photocathode. It is found that the value can be increased up to ∼6 kV/mm and this is used as a design value. Second, as the other method to decrease the photoelectron transit time spread, an electromagnetic focusing method must be adopted because there is no region similar to the focusing section of an electrostatic focusing type where the electric potential is low. Third, the focusing magnetic field should be located in a limited region to obtain a very high sweep speed of ∼2×108 m/s. And fourth, in the operation, a special readjustment of the focusing magnetic field should be performed to compensate the photoelectron beam defocusing caused by the very rapid transient deflection field. Based on the above, a new streak tube has been ...

Use of a gain modulating framing camera for time-resolved imaging of cellular phenomena

A gain modulating framing camera and its application towards the study of real time cellular phenomena is described. Based on a unique operating principle, this framing camera can be modulated by over 90% at 1 GHz. The camera consists of an image converter with a pair of deflection electrodes and a rectangular aperture. Since a sinusoidal electric field is applied to the deflection electrodes, the photoelectron image- forming beam is continuously deflected and swept on the aperture. A bias is applied to center the sweep of the photoelectron beam on the edge of the aperture. The gain modulating with high depth can hence be accomplished. We are now constructing a fluorescence lifetime imaging microscope system employing this gain modulating frame camera based on the phase domain method. Such high depth modulation enables us to achieve frequency signals as low as 1 Hz in heterodyne operation. We describe examples of application of the system towards the observation of various cellular phenomena.

ULTRA‐LOW‐LIGHT LEVEL CAMERA FOR PHOTON COUNTING IMAGING

Abstract— A new ultra‐low‐light level camera svstem has been developed to detect a single photon. Operation principles and some characteristics are presented.

Electron bombardment CCD tube

For low light level imaging application, a proximity focused electron bombardment CCD (EB-CCD) tube has been developed. In the tube, electrons emitted from the multi-alkali (S-20) photocathode in response to incident light are accelerated by the electric field and bombarded the specially processed CCD which is sensitive to electrons. The electron bombardment gain is 600 at applied voltage of -8kV to the photocathode. Single photon counting operation is possible, because the gain is larger than the readout noise and the dark noise of the CCD. The spatial resolution is better than 360 TV lines, which is the theoretical limit of the full frame transfer CCD (FFT-CCD) of 512 by 512 pixels. No major degradation of either the photocathode sensitivity or the incorporated CCD was observed during the operation for a few tens hours. The life of the EB-CCD tube is being under evaluation. Keywords: Electron tube, Photocathode, Image intensifier, Electron-bombardment, CCD, Low light level imaging

Electronic zooming TV readout system for an x-ray microscope

The electronic zooming TV readout system using the x-ray zooming tube has been developed for purposes of real time readout of very high resolution x-ray image, e.g., the output image from an x-ray microscope. The system limiting resolution is 0.2 to approximately 0.3 micrometers and it is easy to operate in practical applications.

Femtosecond streak camera.

Approx. 360fs (femtosecond) of limiting temporal resolution has been obtained with a femtosecond streak camera incorporating a femtosecond streak tube. At the same time, the dynamic range defined by 20% broadening sequence has been observed to be 2.4 at the limiting temporal resolution. In this experiment, a CPM (Colliding-Pulse Mode-locked) ring dye laser which can generate shorter than 100fs pulses at repetition rate of 100MHz has been used. In this paper, performance of the femtosecond streak camera will be discussed in detail.

A Two-Dimensional Photon-Counting Tube

Publisher Summary A photomultiplier tube has been used as a detector for a photoelectron-counting device by making use of its high quantum efficiency and large electron gain coupled with low dark counts. There are demands for a two-dimensional photoelectron-counting imaging in many fields. At very low light levels, a device should incorporate electron multiplication and signal output preserving the input spatial information. To meet these specifications, a two-dimensional photoelectron-counting tube has been developed that has an inverter-type image intensifier structure with a silicon position sensitive device (Si-PSD) instead of a phosphor screen. For applications in the visible wavelength region, a multialkali photocathode was used. This chapter describes the two-dimensional photon-counting tube.

Image reconstruction from an in-line X-ray hologram with intensity distribution constraint

An image reconstruction method for in-line soft X-ray holography is presented. The image is reconstructed by a Fresnel phase-retrieval algorithm using a constraint on the intensity distribution. Experimental results show that the introduction of the intensity constraint is effective for eliminating artifacts such as a twin-image.

X-ray Holographic Microscopy of Biological Specimens with an Electronic Zooming Tube

X-ray holographic microscopy of biological specimens has been performed using in-line holography with the following improvements: (i) an electronic zooming tube is utilized as a detector, and (ii) the object planes are restricted by a metal frame which is not transparent to X-rays at the wavelengths used in the present experiments. The latter modification is useful in computer reconstruction and serves as a reference area where there are no photons in the reconstructed images. This system can minimize the inclusion of errors when recording and reading out holograms compared with methods using an X-ray resist as a detector, or optical reconstruction methods. Two-dimensional images of human cells have been successfully obtained with the present system. Comparison of these images with optical images revealed a good coincidence in structure outlines but not in internal structure images. Holographic observation of HeLa cells at different wavelengths showed a wavelength dependence of the reconstructed images. Since the electronic zooming tube is applicable to a wide range of X-ray wavelengths and has a promising potential to improve its resolution, these results strongly suggest that the present system is a good candidate for the development and establishment of an X-ray holographic microscopy system.

New femtosecond streak camera with temporal resolution of 180 fs

We describe a new design and measure data of a femtosecond streak camera with an electromagnetic focusing type streak tube. In order to reduce the temporal dispersion of photoelectrons in the streak tube, an acceleration electric field near the photocathode was achieved to 8.75 kV/mm applying a high voltage pulse to the dc biased-photocathode. We have developed a high speed deflection circuit and a Meander-type traveling wave deflector, and obtained high sweep speed of 8.76 X 108 m/s on the phosphor screen. A measured data of 180 fs was obtained with 100 photoelectrons using colliding-pulse passively modelocked ring dye laser for the light source. Dynamic ranges of 10 and 20 were achieved at the temporal resolutions of 200 fs and 330 fs, respectively.