Original research articleResearch on imaging system and spatial performance of a pulse-dilation framing camera with larger drift area
Introduction
Framing camera with picoseconds temporal resolution is an ultrafast diagnostic device and mainly utilized to measure the evolutive status of plasmas in the inertial confinement fusion(ICF) [1]. The temporal resolution of an MCP(microchannel plate) framing camera generally is 60–100 ps [2,3]. Although the temporal resolution is improved to approximately 35 ps by the thinner MCP, the dispersion of photoelectron in the MCP limits further enhancement [4].
To break through bottleneck, the framing camera using pulse-dilation technology (PDFC) has been developed, which is capable of achieving up to temporal resolution of 10 ps [5,6]. According to the structure and working principle of PDFC [7,8], the temporal resolution is mainly determined by the accelerating energy, gradient of dilating pulse, drift distance and temporal resolution of MCP ones, which has a nonlinear inverse relationship with the accelerating potential and linearly proportional to the gradient of the dilating pulse [9]. Recently, the PDFC with femtosecond(fs) temporal resolution is achieved by 1.0 m of drift area [10] and gradually approached to the streak camera [11]. With the development of fs PDFC, the future research will be focused on larger drift area, however, whether the spatial performance may up to the previous standards is a questions to be solved, especially, the research on spatial resolution and detection area of PDFC with larger drift area has a special significance, which is the key of fs framing camera.
According to the previously research [[12], [13], [14]], in this paper, we propose an imaging system with triple magnetic lenses. The working principle of PDFC is analyzed, the influence of drift area on spatial performance is theoretically studied. Finally, the larger detection area and high spatial resolution of PDFC with larger drift area are presented.
Section snippets
Working principle of PDFC
The working principle of PDFC is shown as Fig. 1, Firstly, an incoming signal is detected at the photocathode (PC) and converted into photoelectrons(PE). Secondly, the photoelectrons are accelerated through the accelerating area by the negative potential and dilating pulse(time-varying electric field). Subsequently, the photoelectrons transit into the drift area towards the MCP. Thirdly, the acceleration provided by the time-varying electric field decreases as a function of time during the
Imaging system of PDFC with larger drift area
The imaging system of PDFC has been designed by solenoid lens [7] and short focusing magnetic lens [8]. The former has better imaging uniformity and spatial resolution is improved by increasing magnetic field [7]. However, further increasing spatial resolution is limited by high power loss and magnetic saturation, moreover, the solenoid lens is a bulky imaging system and very difficult to adjust imaging ratio; The latter has a simpler system and better spatial resolution in the paraxial region,
Spatial resolution of PDFC
Spatial resolution of PDFC is calculated by the modulation transfer function (MTF) base on the magnetic field and electronic trajectories [13,14], the magnetic field is analyzed by the boundary element method and the electronic trajectories are traced by the RK4 method. The MTF is a plot of modulation as a function of the spatial frequency measured in line pairs/mm. The MTF graph is typically normalized to a value of 1 at zero spatial frequency, which spatial frequency corresponding to contrast
Conclusion
In this work, we propose imaging system of PDFC with a lager drift area that has the potential to achieve better spatial performance. The magnetic field of different drift area are simulated and analyzed. The largest detection area and best spatial resolution of PDFC with larger drift area are discussed. Results show that the magnetic field and spatial performance exhibit opposite trends as a function of drift area. when the accelerating energy is 2 keV and drift area is 0.6 m, the
Declaration of Competing Interest
There are no known conflicts of interest.
Acknowledgments
This work was supported by a grant from the National natural science foundation of China (Nos. 11865007 and 61863008). Natural science foundation of Guangxi (No. 2018GXNSFAA281073). The key project of Guilin University of Electronic Technology (No. JGA201806). Incubation programme of thousand middle younger core teachers of colleges and universities of Guangxi in 2018.
References (16)
- et al.
Investigating the temporal performance of a pulse-dilation framing camera with larger drift area
Optik
(2020) - et al.
Performance evaluation of the imaging system of a pulse-dilation framing camera
Optik
(2019) - et al.
The influence of leakage magnetic slit on imaging performance of framing camera
Optik
(2020) - et al.
Influence of lens aperture size on spatial performance of short magnetic focusing framing camera
Optik
(2020) - et al.
Tracking the movement of the ICF hot spot using the time variance of the shape measured with gated x-ray cameras at NIF
Meccanica
(2013) - et al.
Advances in x-ray framing cameras at the National Ignition Facility to improve quantitative precision in x-ray imaging
Rev. Sci. Instrum.
(2016) - et al.
Gain depletion of X-ray framing camera
Rev. Sci. Instrum.
(2017) - et al.
Development and characterization of a pair of 30-40 ps x-ray framing cameras
Rev. Sci. Instrum.
(1998)