Development of a high-field pulsed magnet and optical fiber coupled cryostat system for magneto-photoluminescence measurements

Abstract

This paper presents the development of a high field pulsed magnet system combined with an optical fiber-coupled low temperature cryostat for magneto-photoluminescence measurements. A novel aspect of our system is the use of electrolyte capacitors in a 75 kJ capacitor bank to drive the pulsed magnet, enabling the generation of high magnetic fields at a relatively low charging voltage (400 V). The zylon reinforced wire wound magnet coil achieves a maximum field strength of 35 tesla with a magnetic field rise time of 10 ms. The integrated cryostat was developed to meet the specific requirements of magneto-photoluminescence experiments using a 4 K helium closed-cycle cryocooler to provide a stable low-temperature environment down to 5 K.

Figures (10)

• Figure 1: (a) Schematic of the pulsed magnetic field generation circuit. (b) Magnetic field profiles recorded at various charging voltages. The inset in panel (b) shows the dependence of the peak magnetic field on the applied charging voltage.
• Figure 1: Pictures of capacitor bank and magnet coil
• Figure 2: Results simulated using the Pulsed Magnet Design Software (PMDS) at a peak magnetic field of 35 T. (a) Schematic of the designed magnet coil, (b) magnetic field profile, (c) radial heating distribution of the coil, and (d) stress distribution as a function of radial distance.
• Figure 2: Clockwise from top left, the images illustrate the assembly process: the bare cryostat mounted on a mechanical aluminum plate, the wiring connected to the cryostat and sample holder, the cryostat enclosed within the vacuum shroud, the optical fiber coupling to the cryostat, the mounted sample holder, and finally the fully assembled cryostat integrated with the pulsed magnet system
• Figure 3: (a) Schematic of the low temperature cryostat mounted on the cryocooler cold head, including the sample holder, the temperature sensors, heater coil, aluminum radiation shield, stainless steel vacuum jacket, electrical and vacuum feedthroughs, optical fiber access, and the liquid nitrogen environment within a polystyrene (styrofoam) container. (b) Enlarged schematic view of the sample holder assembly, highlighting the sample, pickup coil, temperature sensors, heater, sapphire rod and teflon guide. (c) The temperature profiles recorded by a sensor placed at the cryocooler cold head and a sensor at the sapphire rod sample mount. The inset provides a magnified view of the low-temperature region. The sapphire rod sensor reaches a base temperature down to 5 K (blue), while the cold head sensor achieves a minimum temperature of 4.6 K (red).