This work was partially supported by the National Key R&#38;D Program of China (Grant No. 2017YFA0304401) and the National Natural Science Foundation of China (Grant Nos. 11774108, 91336213, and 61875065).

1. Set up the reference directions for polarizers A and B
<ol>
	<li>Put polarizer A and polarizer B into the laser beam (280 nm fourth harmonic laser) path.</li>
	<li>Ensure that the laser beam is perpendicular to the surfaces of the polarizers by carefully adjusting the polarizer holders to keep the back-reflection light coincident with the incident light. 
	NOTE: All the following alignment procedures for the optics components must follow the same rule. The placement of polarizer A and B in the laser path is not important. The spacing between them should be large enough for the future convenient adjustment.</li>
	<li>Put a power meter behind polarizer A and rotate the polarizer to maximize the output power. Define the azimuthal angle (see Results and Discussion) of the optical axis of polarizer A as 0&#176;. Define the clockwise direction as the positive direction and the counterclockwise direction as the negative direction when observing along the direction of light propagation.
	<ol>
		<li>Use a stepper motor rotation stage to hold polarizer A and put the power meter behind polarizer A to record the rotation angles and the output laser powers. Fit the angle vs power curve with a sinusoidal function; the maximum output power position of polarizer A is 0&#176; azimuthal angle position.</li>
	</ol>
	</li>
	<li>Put the power meter behind polarizer B and rotate polarizer B to maximize the output power. The azimuthal angle of the optical axis of polarizer B is then also 0&#176;.
	<ol>
		<li>Use another stepper motor rotation stage to hold polarizer B and put the power meter behind polarizer B to record the rotation angles and the output laser powers. Fit the angle vs power curve with a sinusoidal function; the maximum output power position of polarizer B is 0&#176; azimuthal angle position (see Figure 1).</li>
	</ol>
	</li>
</ol>
2. Set up the reference directions for the azimuthal angles of the waveplates
<ol>
	<li>Put an HWP into the beam path between polarizer A and polarizer B and rotate the HWP to maximize the output power. The azimuthal angle of the optical axis of the HWP is then 0&#176;.
	<ol>
		<li>Use a stepper motor rotation stage to hold the HWP and put the power meter behind polarizer B to record the rotation angles and the output laser powers. Fit the angle vs power curve with a sinusoidal function; the maximum output power position of the HWP is 0&#176; azimuthal angle.</li>
	</ol>
	</li>
	<li>Put a QWP into the beam path between the HWP and polarizer B, rotate the QWP to maximize the output power. The azimuthal angle of the optical axis of the QWP is then 0&#176;.
	<ol>
		<li>Use a stepper motor rotation stage to hold the QWP and put the power meter behind polarizer B to record the rotation angles and the output laser powers. Fit the angle vs power curve with a sinusoidal function; the maximum output power position of the QWP is 0&#176; azimuthal angle position.</li>
	</ol>
	</li>
	<li>Remove polarizer B and the power meter from the beam path. Use two mirrors to direct laser beam into the vacuum chamber that houses an ion trap to interact with 25Mg+ ions. 
	NOTE: The laser propagation direction should be along the magnetic field direction inside the vacuum chamber. A magnetic field is used to define the quantization axis of the ions.</li>
</ol>
3. Doppler cooling of single 25Mg+ ions
<ol>
	<li>Turn on the 532 nm ablation laser, which is a Q-switched Nd:YAG laser. Its repetition rate is 1 kHz, with pulse energy of 150 &#181;J. The ablation laser irradiates a magnesium wire target surface inside the vacuum chamber, and then magnesium (Mg) atoms are ejected from the target surface. 
	NOTE: The power supply for the ion trap should be turned on.</li>
	<li>At the same time, turn on the 285 nm ionization laser to ionized Mg atoms. The ionization laser is a fourth harmonic laser with an output power of 1 mW. The ionization laser will illuminate the center of the ion trap.</li>
	<li>Make sure only one ion is trapped in the ion trap by looking at the image of an electron multiplied charged coupled device (EMCCD). An example image showing trapped ions is shown in Figure 2. Each bright spot is one ion. If there is more than one ion in the trap, turn off the power supply of the ion trap to release the ions. Then repeat steps 3.1-3.2 until only one (i.e., single) ion is trapped. 
	NOTE: The homemade imaging system of the EMCCD consists of four lenses, and its magnification is 10x. The ion spacing is about 2-10 &#181;m and the pixel spacing of the EMCCD is 16 &#181;m. The EMCCD can, therefore, be used to identify the existence of one single ion.</li>
	<li>Set the magnetic field to be 6.5 Gauss by adjusting the current of Helmholtz coils. The magnetic field is measured by comparing the different frequencies between the two ground state transitions, <img align="center" alt="Equation" src="/files/ftp_upload/61175/61175eq1.jpg" /> and <img align="center" alt="Equation" src="/files/ftp_upload/61175/61175eq2.jpg" />. For details of the method please refer11.</li>
</ol>
4. Lock the 280 nm Doppler cooling laser frequency to a wavelength meter12
<ol>
	<li>Scan the frequency of the 280 nm laser and count the fluorescence photon numbers collected by a photon multiplier tube (PMT) by a frequency counter. At the same time, record the frequency of the laser using a wavelength meter. Find the resonant frequency &#957;0 where the fluorescence rate reaches a maximum. 
	NOTE: The fluorescence counts will increase when the laser frequency is moving close to the ion resonant frequency and will reach a maximum at the resonant frequency <img align="center" alt="Equation" src="/files/ftp_upload/61175/61175eq3.jpg" />.</li>
	<li>Lock the laser frequency to the wavelength meter using a digital servo control program that is running on an accompanying computer. Click on the Lock button on the program graphic interface when the wavelength meter shows a reading of <img align="center" alt="Equation" src="/files/ftp_upload/61175/61175eq3.jpg" />.</li>
</ol>
5. Set the intensity of the laser to equal the saturation intensity12
<ol>
	<li>Change the power of the laser by adjusting the driving power of an acousto-optic-modulator (AOM), which is used in the beam path to change the frequency and power of the laser. Record the power and the fluorescence counts.</li>
	<li>Fit the curve of the power and the fluorescence counts with Equation (6), and obtain the saturation power <img align="center" alt="Equation" src="/files/ftp_upload/61175/61175eq4a.jpg" />.</li>
	<li>Set the laser power to <img align="center" alt="Equation" src="/files/ftp_upload/61175/61175eq4a.jpg" /> by adjusting the driving power of the AOM.</li>
</ol>
6. Measure the birefringence of the vacuum window.
<ol>
	<li>Alternately, adjust the azimuthal angles of the HWP and the QWP to maximize the fluorescence counts. Record the azimuthal angles of the HWP and the QWP at maximum counts, which are &#945; and &#946;.
	<ol>
		<li>Use the stepper motor rotation stages to rotate the HWP and the QWP and record the rotation angles and the corresponding fluorescence counts.</li>
	</ol>
	</li>
	<li>Use Equation (4) and Equation (5) to calculate the birefringence of the vacuum window &#952; and <img alt="Equation" src="/files/ftp_upload/61175/61175eq5.jpg" />.</li>
</ol>

<ol>
	<li>Robens, C., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=High-Precision+Optical+Polarization+Synthesizer+for+Ultracold-Atom+Experiments.">High-Precision Optical Polarization Synthesizer for Ultracold-Atom Experiments.</a> Physical Review A. 9 (3), 34016 (2018).</li><li>Cairncross, W. B., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Precision+Measurement+of+the+Electron's+Electric+Dipole+Moment+Using+Trapped+Molecular+Ions.">Precision Measurement of the Electron's Electric Dipole Moment Using Trapped Molecular Ions.</a> Physical Review Letters. 119 (15), 153001 (2017).</li><li>Bougas, L., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Fundamentals+of+cavity-enhanced+polarimetry+for+parity-nonconserving+optical+rotation+measurements:+Application+to+Xe,+Hg,+and+I.">Fundamentals of cavity-enhanced polarimetry for parity-nonconserving optical rotation measurements: Application to Xe, Hg, and I.</a> Physical Review A. 89 (5), 52127 (2014).</li><li>Bragin, S., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=High-Energy+Vacuum+Birefringence+and+Dichroism+in+an+Ultra-strong+Laser+Field.">High-Energy Vacuum Birefringence and Dichroism in an Ultra-strong Laser Field.</a> Physical Review Letters. 119 (25), 250403 (2017).</li><li>Nicholson, T. 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The authors have nothing to disclose.

This manuscript describes a method to perform in situ measurement of the birefringence of the vacuum window and the polarization states of the laser light inside the vacuum chamber. By adjusting the azimuthal angles of the HWP and the QWP (&#945; and &#946;), the effect of the birefringence of the vacuum window (&#948; and &#952;) can be compensated so that the laser inside the vacuum chamber is a pure circularly polarized light. At this point, there exists a definite relationship between the birefringence of the vacuum ...

In many research fields such as cold atom experiments1, measurement of the electric dipole moment2, test of parity-nonconservation3, measurement of vacuum birefringence4, optical clocks5, quantum optics experiments6, and liquid crystal study7, it is important to precisely measure and accurately control the polarization states of laser light.
In experiments involving the use of a vacuum environment, the stress-induced birefringence effect of vacuum windows will affect the polarization states of laser light. It is not feasible to put a polarization analyzer inside the vacuum chamber to directly measure the polarization states of the laser light. One solution is to use atoms or ions directly as an in situ polarization analyzer to analyze the birefringence of vacuum windows. The vector light shifts of Cs atoms8 are sensitive to the degrees of linear polarization of the incidence laser light9. But this method is time consuming and can only be applied to the linearly polarized laser light detection.
Presented is a new, quick, precise, in situ method to determine the polarization states of laser light inside the vacuum chamber based on maximizing single 25Mg+ fluorescence in an ion trap. The method is based on the relationship of the ion fluorescence to the polarization states of the laser light, which is affected by the birefringence of the vacuum window. The proposed method is used for detecting the birefringence of vacuum windows and degrees of circular polarization of laser light inside a vacuum chamber10.
The method is applicable to any atoms or ions whose fluorescence rate is sensitive to the polarization states of laser light. In addition, while the demonstration is used to prepare a pure circularly polarized light, with the knowledge of the birefringence of the vacuum window, arbitrary polarization states of laser light can be prepared inside the vacuum chamber. Therefore, the method is quite useful for a wide range of experiments.

<table border="1" fo:keep-together.within-page="1" fo:keep-with-next.within-page="always">
	<tbody>
		<tr>
			<td>280 nm Doppler cooling laser</td>
			<td>Toptica</td>
			<td>SYST DL-FHG Pro 280</td>
			<td>Doppler cooling laser</td>
		</tr>
		<tr>
			<td>285 nm ionization laser</td>
			<td>Toptica</td>
			<td>SYST DL-FHG Pro 285</td>
			<td>ionization laser</td>
		</tr>
		<tr>
			<td>Ablation laser</td>
			<td>Changchun New Industries Optoelectronics Technology</td>
			<td>EL-532-1.5W</td>
			<td>Q-switched Nd:YAG laser</td>
		</tr>
		<tr>
			<td>AOM</td>
			<td>Gooch &#38; Housego</td>
			<td>AOMO 3200-1220</td>
			<td>wavelengh down to 257 nm</td>
		</tr>
		<tr>
			<td>EMCCD camera</td>
			<td>Andor</td>
			<td>iXon3 897</td>
			<td>imaging of 25Mg+ in ion trap</td>
		</tr>
		<tr>
			<td>Glan-Taylor polarizer</td>
			<td>Union Optic</td>
			<td>Custom</td>
			<td>distinction ratio 1e-6</td>
		</tr>
		<tr>
			<td>Half waveplate</td>
			<td>Union Optic</td>
			<td>Custom</td>
			<td>made of quartz</td>
		</tr>
		<tr>
			<td>Photon multiplier tube</td>
			<td>Hamamatsu</td>
			<td>H8259-09</td>
			<td>fluorescent counting</td>
		</tr>
		<tr>
			<td>Power meter</td>
			<td>Thorlabs</td>
			<td>PM100D</td>
			<td>laser power monitor</td>
		</tr>
		<tr>
			<td>Quarter waveplate</td>
			<td>Union Optic</td>
			<td>Custom</td>
			<td>made of quartz</td>
		</tr>
		<tr>
			<td>Mirror</td>
			<td>Union Optic</td>
			<td>Custom</td>
			<td>dielectric coated for 280 nm</td>
		</tr>
		<tr>
			<td>Stepper motor roation stage</td>
			<td>Thorlabs</td>
			<td>K10CR1/M</td>
			<td>rotating wave plates</td>
		</tr>
		<tr>
			<td>Vacuum chamber</td>
			<td>Kimball Physics</td>
			<td>MCF800-SphSq-G2E4C4</td>
			<td>made of Titanium</td>
		</tr>
		<tr>
			<td>Vacuum window</td>
			<td>Union Optic</td>
			<td>Custom</td>
			<td>made of fused silica</td>
		</tr>
	</tbody>
</table>

in situ measurement of vacuum window birefringence using 25mg+ fluorescence

Accurate control of the polarization states of laser light is important in precision measurement experiments. In experiments involving the use of a vacuum environment, the stress-induced birefringence effect of the vacuum windows will affect the polarization states of laser light inside the vacuum system, and it is very difficult to measure and optimize the polarization states of the laser light in situ. The purpose of this protocol is to demonstrate how to optimize the polarization states of the laser light based on the fluorescence of ions in the vacuum system, and how to calculate the birefringence of vacuum windows based on azimuthal angles of external wave plates with Mueller matrix. The fluorescence of 25Mg+ ions induced by laser light that is resonant with the transition of |32P3/2,F = 4, mF&#160;= 4<img align="center" alt="Equation 100" src="/files/ftp_upload/61175/61175img1.jpg" style="color: rgb(68, 0, 68); font-size: 18px; font-weight: 700;" />&#160;&#8594;&#160;|32S1/2,F = 3, mF&#160;= 3<img align="center" alt="Equation 100" src="/files/ftp_upload/61175/61175img1.jpg" style="color: rgb(68, 0, 68); font-size: 18px; font-weight: 700;" />&#160;is sensitive to the polarization state of the laser light, and maximum fluorescence will be observed with pure circularly polarized light. A combination of half-wave plate (HWP) and quarter-wave plate (QWP) can achieve arbitrary phase retardation and is used for compensating the birefringence of the vacuum window. In this experiment, the polarization state of the laser light is optimized based on the fluorescence of 25Mg+ ion with a pair of HWP and QWP outside the vacuum chamber. By adjusting the azimuthal angles of the HWP and QWP to obtain maximum ion fluorescence, one can obtain a pure circularly polarized light inside the vacuum chamber. With the information on the azimuthal angles of the external HWP and QWP, the birefringence of the vacuum window can be determined.

Figure 3 shows the beam path of the experiment. Polarizer B in Figure 3a is removed after angle initialization (Figure 3b). The laser passed through a polarizer, an HWP, a QWP, and the vacuum window, sequentially. The Stokes vector of laser is <img align="center" alt="Equation" src="/files/ftp_upload/61175/61175eq6.jpg" />, where <img align="center" alt="Equation" sr...

Watch this Scientific Journal Video about In Situ Measurement of Vacuum Window Birefringence using 25Mg+ Fluorescence at JoVE.com

In Situ Measurement of Vacuum Window Birefringence using 25Mg+ Fluorescence

Presented here is a method to measure the birefringence of vacuum windows by maximizing the fluorescence counts emitted by Doppler cooled 25Mg+ ions in an ion trap. The birefringence of vacuum windows will change the polarization states of the laser, which can be compensated by changing the azimuthal angles of external wave plates.

In Situ Measurement of Vacuum Window Birefringence using 25Mg+ Fluorescence

Accurate control of the polarization states of laser light is important in precision measurement experiments. In experiments involving the use of a vacuum ...

in-situ-measurement-vacuum-window-birefringence-using-25mg

Universidad de Cartagena UDEC

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3.8K Views.  Huazhong University of Science and Technology. Presented here is a method to measure the birefringence of vacuum windows by maximizing the fluorescence counts emitted by Doppler cooled 25Mg+ ions in an ion trap. The birefringence of vacuum windows will change the polarization states of the laser, which can be compensated by changing the azimuthal angles of external wave plates.

Video: In Situ Measurement of Vacuum Window Birefringence using 25Mg+ Fluorescence

Measurement of Coherence Decay in GaMnAs Using Femtosecond Four-wave Mixing

The application of femtosecond four-wave mixing to the study of fundamental properties of diluted magnetic semiconductors ((s,p)-d hybridization, spin-flip scattering) is described, using experiments on GaMnAs as a prototype III-Mn-V system.&#160; Spectrally-resolved and time-resolved experimental configurations are described, including the use of zero-background autocorrelation techniques for pulse optimization.&#160; The etching process used to prepare GaMnAs samples for four-wave mixing experiments is also highlighted.&#160; The high temporal resolution of this technique, afforded by the use of short (20 fsec) optical pulses, permits the rapid spin-flip scattering process in this system to be studied directly in the time domain, providing new insight into the strong exchange coupling responsible for carrier-mediated ferromagnetism.&#160; We also show that spectral resolution of the four-wave mixing signal allows one to extract clear signatures of (s,p)-d hybridization in this system, unlike linear spectroscopy techniques.&#160;&#160; This increased sensitivity is due to the nonlinearity of the technique, which suppresses defect-related contributions to the optical response. This method may be used to measure the time scale for coherence decay (tied to the fastest scattering processes) in a wide variety of semiconductor systems of interest for next generation electronics and optoelectronics.

The technique of femtosecond four-wave mixing is described, including spectrally-resolved and time-resolved configurations. We illustrate the utility of this technique for the investigation of crucial physical properties in the III-V diluted magnetic semiconductors, afforded by its nonlinearity and high temporal resolution.

The application of femtosecond four-wave mixing to the study of fundamental properties of diluted magnetic semiconductors ((s,p)-d hybridization, ...

In Situ Neutron Powder Diffraction Using Custom-made Lithium-ion Batteries

Li-ion batteries are widely used in portable electronic devices and are considered as promising candidates for higher-energy applications such as electric vehicles.1,2 However, many challenges, such as energy density and battery lifetimes, need to be overcome before this particular battery technology can be widely implemented in such applications.3 This research is challenging, and we outline a method to address these challenges using in situ NPD to probe the crystal structure of electrodes undergoing electrochemical cycling (charge/discharge) in a battery. NPD data help determine the underlying structural mechanism responsible for a range of electrode properties, and this information can direct the development of better electrodes and batteries.
We briefly review six types of battery designs custom-made for NPD experiments and detail the method to construct the &#8216;roll-over&#8217; cell that we have successfully used on the high-intensity NPD instrument, WOMBAT, at the Australian Nuclear Science and Technology Organisation (ANSTO). The design considerations and materials used for cell construction are discussed in conjunction with aspects of the actual in situ NPD experiment and initial directions are presented on how to analyze such complex in situ data.

In Situ Neutron Powder Diffraction Using Custom-made Lithium-ion Batteries

We describe the design and construction of an electrochemical cell for the examination of electrode materials using in situ neutron powder diffraction (NPD). We briefly comment on alternate in situ NPD cell designs and discuss methods for the analysis of the corresponding in situ NPD data produced using this cell.

Li-ion batteries are widely used in portable electronic devices and are considered as promising candidates for higher-energy applications such as electric ...

Development of an Experimental Setup for the Measurement of the Coefficient of Restitution under Vacuum Conditions

The Discrete Element Method is used for the simulation of particulate systems to describe and analyze them, to predict and afterwards optimize their behavior for single stages of a process or even an entire process. For the simulation with occurring particle-particle and particle-wall contacts, the value of the coefficient of restitution is required. It can be determined experimentally. The coefficient of restitution depends on several parameters like the impact velocity. Especially for fine particles the impact velocity depends on the air pressure and under atmospheric pressure high impact velocities cannot be reached. For this, a new experimental setup for free-fall tests under vacuum conditions is developed. The coefficient of restitution is determined with the impact and rebound velocity which are detected by a high-speed camera. To not hinder the view, the vacuum chamber is made of glass. Also a new release mechanism to drop one single particle under vacuum conditions is constructed. Due to that, all properties of the particle can be characterized beforehand.

The coefficient of restitution is a parameter that describes the loss of kinetic energy during collision. Here, a free-fall setup under vacuum conditions is developed to be able to determine the coefficient of restitution parameter for particles in micrometer range with high impact velocities.

The Discrete Element Method is used for the simulation of particulate systems to describe and analyze them, to predict and afterwards optimize their ...

Seedless Growth of Bismuth Nanowire Array via Vacuum Thermal Evaporation

Here a seedless and template-free technique is demonstrated to scalably grow bismuth nanowires, through thermal evaporation in high vacuum at RT. Conventionally reserved for the fabrication of metal thin films, thermal evaporation deposits bismuth into an array of vertical single crystalline nanowires over a flat thin film of vanadium held at RT, which is freshly deposited by magnetron sputtering or thermal evaporation. By controlling the temperature of the growth substrate the length and width of the nanowires can be tuned over a wide range. Responsible for this novel technique is a previously unknown nanowire growth mechanism that roots in the mild porosity of the vanadium thin film. Infiltrated into the vanadium pores, the bismuth domains (~ 1 nm) carry excessive surface energy that suppresses their melting point and continuously expels them out of the vanadium matrix to form nanowires. This discovery demonstrates the feasibility of scalable vapor phase synthesis of high purity nanomaterials without using any catalysts.

A protocol for seedless and high yield growth of bismuth nanowire arrays through vacuum thermal evaporation technique is presented.

Here a seedless and template-free technique is demonstrated to scalably grow bismuth nanowires, through thermal evaporation in high vacuum at RT. ...

Optical Trap Loading of Dielectric Microparticles In Air

We demonstrate a method to trap a selected dielectric microparticle in air using radiation pressure from a single-beam gradient optical trap. Randomly scattered dielectric microparticles adhered to a glass substrate are momentarily detached using ultrasonic vibrations generated by a piezoelectric transducer (PZT). Then, the optical beam focused on a selected particle lifts it up to the optical trap while the vibrationally excited microparticles fall back to the substrate. A particle may be trapped at the nominal focus of the trapping beam or at a position above the focus (referred to here as the levitation position) where gravity provides the restoring force. After the measurement, the trapped particle can be placed at a desired position on the substrate in a controlled manner. 
In this protocol, an experimental procedure for selective optical trap loading in air is outlined. First, the experimental setup is briefly introduced. Second, the design and fabrication of a PZT holder and a sample enclosure are illustrated in detail. The optical trap loading of a selected microparticle is then demonstrated with step-by-step instructions including sample preparation, launching into the trap, and use of electrostatic force to excite particle motion in the trap and measure charge. Finally, we present recorded particle trajectories of Brownian and ballistic motions of a trapped microparticle in air. These trajectories can be used to measure stiffness or to verify optical alignment through time domain and frequency domain analysis. Selective trap loading enables optical tweezers to track a particle and its changes over repeated trap loadings in a reversible manner, thereby enabling studies of particle-surface interaction.

A protocol for launching and stably trapping selected dielectric microparticles in air is presented.

We demonstrate a method to trap a selected dielectric microparticle in air using radiation pressure from a single-beam gradient optical trap. Randomly ...

Standardized Method for Measuring Collection Efficiency from Wipe-sampling of Trace Explosives

One of the limiting steps to detecting traces of explosives at screening venues is effective collection of the sample. Wipe-sampling is the most common procedure for collecting traces of explosives, and standardized measurements of collection efficiency are needed to evaluate and optimize sampling protocols. The approach described here is designed to provide this measurement infrastructure, and controls most of the factors known to be relevant to wipe-sampling. Three critical factors (the applied force, travel distance, and travel speed) are controlled using an automated device. Test surfaces are chosen based on similarity to the screening environment, and the wipes can be made from any material considered for use in wipe-sampling. Particle samples of the explosive 1,3,5-trinitroperhydro-1,3,5-triazine (RDX) are applied in a fixed location on the surface using a dry-transfer technique. The particle samples, recently developed to simulate residues made after handling explosives, are produced by inkjet printing of RDX solutions onto polytetrafluoroethylene (PTFE) substrates. Collection efficiency is measured by extracting collected explosive from the wipe, and then related to critical sampling factors and the selection of wipe material and test surface. These measurements are meant to guide the development of sampling protocols at screening venues, where speed and throughput are primary considerations.

Optimized sampling protocols and the development of new wipe materials can be facilitated by standardized measurements of collection efficiency from wipe-sampling. Our approach for sampling trace explosives uses an automated device to control speed, force, and distance during wipe-sampling followed by extraction of collected explosives.

One of the limiting steps to detecting traces of explosives at screening venues is effective collection of the sample. Wipe-sampling is the most common ...

Production and Characterization of Vacuum Deposited Organic Light Emitting Diodes

A method for producing simple and efficient thermally-activated delayed fluorescence organic light-emitting diodes (OLEDs) based on guest-host or exciplex donor-acceptor emitters is presented. With a step-by-step procedure, readers will be able to repeat and produce OLED devices based on simple organic emitters. A patterning procedure allowing the creation of personalized indium tin oxide (ITO) shape is shown. This is followed by the evaporation of all layers, encapsulation and characterization of each individual device. The end goal is to present a procedure that will give the opportunity to repeat the information presented in cited publication but also using different compounds and structures in order to prepare efficient OLEDs.

A protocol for the production of simple structured organic light-emitting diodes (OLEDs) is presented.

A method for producing simple and efficient thermally-activated delayed fluorescence organic light-emitting diodes (OLEDs) based on guest-host or exciplex ...

Generation of Size-controlled Poly (ethylene Glycol) Diacrylate Droplets via Semi-3-Dimensional Flow Focusing Microfluidic Devices

Uniform and size-controllable poly (ethylene glycol) diacrylate (PEGDA) droplets could be produced via the flow focusing process in a microfluidic device. This paper proposes a semi-three-dimensional (semi-3D) flow-focusing microfluidic chip for droplet formation. The polydimethylsiloxane (PDMS) chip was fabricated using the multi-layer soft lithography method. Hexadecane containing surfactant was used as the continuous phase, and PEGDA with the ultraviolet (UV) photo-initiator was the dispersed phase. Surfactants allowed the local surface tension to drop and formed a more cusped tip which promoted breaking into tiny micro-droplets. As the pressure of dispersed phase was constant, the size of droplets became smaller with increasing continuous phase pressure before dispersed phase flow was broken off. As a result, droplets with size variation from 1 &#181;m to 80 &#181;m in diameter could be selectively achieved by changing the pressure ratio in two inlet channels, and the average coefficient of variation was estimated to be below 7%. Furthermore, droplets could turn into micro-beads by UV exposure for photo-polymerization. Conjugating biomolecules on such micro-beads surface have many potential applications in the fields of biology and chemistry.

Generation of Size-controlled Poly ethylene Glycol Diacrylate Droplets via Semi-3-Dimensional Flow Focusing Microfluidic Devices

Here, we present a protocol to illustrate the fabrication processes and verifying experiments of a semi-three-dimensional (semi-3D) flow-focusing microfluidic chip for droplet formation.

Uniform and size-controllable poly (ethylene glycol) diacrylate (PEGDA) droplets could be produced via the flow focusing process in a microfluidic device. ...

Methods of Ex Situ and In Situ Investigations of Structural Transformations: The Case of Crystallization of Metallic Glasses

We demonstrate the use of two nuclear-based analytical methods that can follow the modifications of microstructural arrangement of iron-based metallic glasses (MGs). Despite their amorphous nature, the identification of hyperfine interactions unveils faint structural modifications. For this purpose, we have employed two techniques that utilize nuclear resonance among nuclear levels of a stable 57Fe isotope, namely M&#246;ssbauer spectrometry and nuclear forward scattering (NFS) of synchrotron radiation. The effects of heat treatment upon (Fe2.85Co1)77Mo8Cu1B14 MG are discussed using the results of ex situ and in situ experiments, respectively. As both methods are sensitive to hyperfine interactions, information on structural arrangement as well as on magnetic microstructure is readily available. M&#246;ssbauer spectrometry performed ex situ describes how the structural arrangement and magnetic microstructure appears at room temperature after the annealing under certain conditions (temperature, time), and thus this technique inspects steady states. On the other hand, NFS data are recorded in situ during dynamically changing temperature and NFS examines transient states. The use of both techniques provides complementary information. In general, they can be applied to any suitable system in which it is important to know its steady state but also transient states.

Methods of Ex Situ and In Situ Investigations of Structural Transformations: The Case of Crystallization of Metallic Glasses

Here, we present a protocol to describe ex situ and in situ investigations of structural transformations in metallic glasses. We employed nuclear-based analytical methods which inspect hyperfine interactions. We demonstrate the applicability of M&#246;ssbauer spectrometry and nuclear forward scattering of synchrotron radiation during temperature-driven experiments.

We demonstrate the use of two nuclear-based analytical methods that can follow the modifications of microstructural arrangement of iron-based metallic ...

Method Development for Contactless Resonant Cavity Dielectric Spectroscopic Studies of Cellulosic Paper

The current analytical techniques for characterizing printing and graphic arts substrates are largely ex situ and destructive. This limits the amount of data that can be obtained from an individual sample and renders it difficult to produce statistically relevant data for unique and rare materials. Resonant cavity dielectric spectroscopy is a non-destructive, contactless technique which can simultaneously interrogate both sides of a sheeted material and provide measurements which are suitable for statistical interpretations. This offers analysts the ability to quickly discriminate between sheeted materials based on composition and storage history. In this methodology article, we demonstrate how contactless resonant cavity dielectric spectroscopy may be used to differentiate between paper analytes of varying fiber species compositions, to determine the relative age of the paper, and to detect and quantify the amount of post-consumer waste (PCW) recycled fiber content in manufactured office paper.

A protocol for the non-destructive analysis of the fiber content and relative age of paper.

The current analytical techniques for characterizing printing and graphic arts substrates are largely ex situ and destructive. This limits the amount of ...

In Situ Measurement of Vacuum Window Birefringence using ²⁵Mg⁺ Fluorescence

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Chapters in this video

Measurement of Coherence Decay in GaMnAs Using Femtosecond Four-wave Mixing

In Situ Neutron Powder Diffraction Using Custom-made Lithium-ion Batteries

Development of an Experimental Setup for the Measurement of the Coefficient of Restitution under Vacuum Conditions

Seedless Growth of Bismuth Nanowire Array via Vacuum Thermal Evaporation

Optical Trap Loading of Dielectric Microparticles In Air

Standardized Method for Measuring Collection Efficiency from Wipe-sampling of Trace Explosives

Production and Characterization of Vacuum Deposited Organic Light Emitting Diodes

Generation of Size-controlled Poly (ethylene Glycol) Diacrylate Droplets via Semi-3-Dimensional Flow Focusing Microfluidic Devices

Methods of Ex Situ and In Situ Investigations of Structural Transformations: The Case of Crystallization of Metallic Glasses

Method Development for Contactless Resonant Cavity Dielectric Spectroscopic Studies of Cellulosic Paper