arXiv subjects

J. Scherschligt

Publications and source records attributed to J. Scherschligt.

9 recordsLinked to original sources

arXiv2022

A constant pressure flowmeter for extreme-high vacuum

We demonstrate operation of a constant-pressure flowmeter capable of generating and accurately measuring flows as low as $2\times10^{-13}$ mol/s. Generation of such small flows is accomplished by using a small conductance element with $C\approx 50$ nL/s. Accurate measurement then requires both low outgassing materials ($<10^{-15}$ mol/s) and small volume changes ($\approx 70$ $μ$L). We outline the present flowmeter's construction, detail its operation, and quantify its uncertainty. The type-B uncertainty is $<0.2$ % ($k=1$) over the entire operating range. In particular, we present an analysis of its hydraulic system, and quantify the shift and uncertainty due to the slightly compressible oil. Finally, we compare our flowmeter against a NIST standard flowmeter, and find agreement to within 0.5 % ($k=2$).

physics.ins-det↗

arXiv2021

$Λ$-enhanced gray molasses in a tetrahedral laser beam geometry

We report observation of sub-Doppler cooling of lithium using an irregular-tetrahedral laser beam arrangement, which is produced by a nanofabricated diffraction grating. We are able to capture 11(2) % of the lithium atoms from a grating magneto-optical trap into $Λ$-enhanced $D_1$ gray molasses. The molasses cools the captured atoms to a radial temperature of 60(9) $μ$K and an axial temperature of 23(3) $μ$K. In contrast to results from conventional counterpropagating beam configurations, we do not observe cooling when our optical fields are detuned from Raman resonance. An optical Bloch equation simulation of the cooling dynamics agrees with our data. Our results show that grating magneto-optical traps can serve as a robust source of cold atoms for tweezer-array and atom-chip experiments, even when the atomic species is not amenable to sub-Doppler cooling in bright optical molasses.

physics.atom-ph↗

arXiv2021

A Bitter-type electromagnet for complex atomic trapping and manipulation

We create a pair of symmetric Bitter-type electromagnet assemblies capable of producing multiple field configurations including uniform magnetic fields, spherical quadruple traps, or Ioffe-Pritchard magnetic bottles. Unlike other designs, our coil allows both radial and azimuthal cooling water flows by incorporating an innovative 3D-printed water distribution manifold. Combined with a double-coil geometry, such orthogonal flows permit stacking of non-concentric Bitter coils. We achieve a low thermal resistance of 4.2(1) K/kW and high water flow rate of 10.0(3) L/min at a pressure of 190(10) kPa.

physics.ins-det↗

arXiv2020

PyLCP: A python package for computing laser cooling physics

We present a python object-oriented computer program for simulating various aspects of laser cooling physics. Our software is designed to be both easy to use and adaptable, allowing the user to specify the level structure, magnetic field profile, or the laser beams' geometry, detuning, and intensity. The program contains three levels of approximation for the motion of the atom, applicable in different regimes offering cross checks for calculations and computational efficiency depending on the physical situation. We test the software by reproducing well-known phenomena, such as damped Rabi flopping, electromagnetically induced transparency, stimulated Raman adiabatic passage, and optical molasses. We also use our software package to quantitatively simulate recoil-limited magneto-optical traps, like those formed on the narrow $^1$S$_0\rightarrow ^3$P$_1$ transition in $^{88}$Sr and $^{87}$Sr.

physics.atom-ph↗

arXiv2020

A radiofrequency voltage-controlled current source for quantum spin manipulation

We present a design for a wide-bandwidth, voltage-controlled current source that is easily integrated with radiofrequency magnetic field coils. Our design uses current feedback to compensate for the frequency-dependent impedance of a radiofrequency antenna. We are able to deliver peak currents greater than 100 mA over a 300 kHz to 54 MHz frequency span. The radiofrequency current source fits onto a printed circuit board smaller than $4~\text{cm}^2$ and consumes less than 1.3 W of power. It is suitable for use in deployable quantum sensors and nuclear-magnetic-resonance systems.

physics.ins-det↗

arXiv2019

A flexible, open-source radio-frequency driver for acousto-optic and electro-optic devices

We present a design for a radio-frequency driver that leverages telecom amplifiers to achieve high power output and wide bandwidth. The design consists of two compact printed circuit boards (total area $< 255$ cm), which incorporate power (turn-on) and thermal management to prevent accidental damage to the amplifier circuitry. Our driver provides $>1$ W of output power over a $10$ MHz to $1.1$ GHz frequency range, and $\geq 5$ W from $20$ MHz to $100$ MHz. The driver circuit includes auxiliary components for analog frequency and amplitude modulation ($\approx 70$ kHz bandwidth), as well as digital power switching ($> 30$ dB of extinction within $40$ ns and final extinction $> 90$ dB). The radio-frequency source can also be digitally switched between an external input and an integrated voltage-controlled oscillator. Our design is motivated by the need for flexible, inexpensive drivers of optically active devices, such as acousto-optic and electro-optic modulators.

physics.ins-det↗

arXiv2019

Single-beam Zeeman slower and magneto-optical trap using a nanofabricated grating

We demonstrate a compact (0.25 L) system for laser cooling and trapping atoms from a heated dispenser source. Our system uses a nanofabricated diffraction grating to generate a magneto-optical trap (MOT) using a single input laser beam. An aperture in the grating allows atoms from the dispenser to be loaded from behind the chip, increasing the interaction distance of atoms with the cooling light. To take full advantage of this increased distance, we extend the magnetic field gradient of the MOT to create a Zeeman slower. The MOT traps approximately $10^6$ $^7$Li atoms emitted from an effusive source with loading rates in excess of $10^6$ s$^{-1}$. Our design is portable to a variety of atomic and molecular species and could be a principal component of miniaturized cold-atom-based technologies.

physics.atom-ph↗

arXiv2018

Light-induced atomic desorption of lithium

We demonstrate loading of a Li magneto-optical trap using light-induced atomic desorption. The magneto-optical trap confines up to approximately $4\times10^{4}$ $^{7}\text{Li}$ atoms with loading rates up to approximately $4\times10^{3}$ atoms per second. We study the Li desorption rate as a function of the desorption wavelength and power. The extracted wavelength threshold for desorption of Li from fused silica is approximately $470$ nm. In addition to desorption of lithium, we observe light-induced desorption of background gas molecules. The vacuum pressure increase due to the desorbed background molecules is $\lesssim50$ % and the vacuum pressure decreases back to its base value with characteristic timescales on the order of seconds when we extinguish the desorption light. By examining both the loading and decay curves of the magneto-optical trap, we are able to disentangle the trap decay rates due to background gases and desorbed lithium. Our results show that light-induced atomic desorption can be a viable Li vapor source for compact devices and sensors.

physics.atom-ph↗

arXiv2004

High-Temperature Hall Effect in Ga(1-x)Mn(x)As

The temperature dependence of the Hall coefficient of a series of ferromagnetic Ga(1-x)Mn(x)As samples is measured in the temperature range 80K < T < 500K. We model the Hall coefficient assuming a magnetic susceptibility given by the Curie-Weiss law, a spontaneous Hall coefficient proportional to rho_xx^2(T), and including a constant diamagnetic contribution in the susceptibility. For all low resistivity samples this model provides excellent fits to the measured data up to T=380K and allows extraction of the hole concentration (p). The calculated p are compared to alternative methods of determining hole densities in these materials: pulsed high magnetic field (up to 55 Tesla) technique at low temperatures (less than the Curie temperature), and electrochemical capacitance- voltage profiling. We find that the Anomalous Hall Effect (AHE) contribution to rho_xy is substantial even well above the Curie temperature. Measurements of the Hall effect in this temperature regime can be used as a testing ground for theoretical descriptions of transport in these materials. We find that our data are consistent with recently published theories of the AHE, but they are inconsistent with theoretical models previously used to describe the AHE in conventional magnetic materials.

cond-mat.mtrl-sci↗