Name: automated delivery of microfabricated targets for intense laser irradiation experiments
Uploaded: 2021-01-28T13:00:00
Description: Watch this Scientific Journal Video about Automated Delivery of Microfabricated Targets for Intense Laser Irradiation Experiments at JoVE.com

This work has been supported by the Israel Science Foundation, grant No. 1135/15 and by the Zuckerman STEM Leadership Program, Israel, which are gratefully acknowledged. We also acknowledge the support of the Pazy Foundation, Israel grant #27707241, and NSF-BSF grant No. 01025495.&#160;The authors would like to kindly acknowledge Tel Aviv University Center for Nanoscience and Nanotechnolog

1. Target fabrication
NOTE: Figure 2 and Figure 3 illustrate the fabrication process of freestanding gold foils.
<ol>
	<li>Back Side
	<ol>
		<li>Use a 250 &#956;m thick, 100 mm diameter, high-stress silicon wafer in a &#60;100&#62; crystal formation, coated on both sides with silicon nitride.</li>
		<li>Clean the wafer using acetone&#160;followed by isopropanol and dry with nitrogen.&#160; Then spin coat a layer of HMDS&#160;to form...

<ol>
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A., 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=Intense+High-Energy+Proton+Beams+from+Petawatt-Laser+Irradiation+of+Solids.">Intense High-Energy Proton Beams from Petawatt-Laser Irradiation of Solids.</a> Physical Review Letters. 85, 4945 (2000).</li><li>Tosaki, 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=Evaluation+of+laser-driven+ion+energies+for+fusion+fast-ignition+research.">Evaluation of laser-driven ion energies for fusion fast-ignition research.</a> Progress of Theoretical and Experimental Physics. 2017 (10), 103 (2017).</li><li>Borghesi, M., 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=Proton+imaging:+a+diagnostic+for+inertial+confinement+fusion/fast+ignitor+studies+Related+content+Inertial+confinement+fusion+and+fast+ignitor+studies.">Proton imaging: a diagnostic for inertial confinement fusion/fast ignitor studies Related content Inertial confinement fusion and fast ignitor studies.</a> Plasma Physics and Controlled Fusion. 43, 12 (2001).</li><li>Malka, V., 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=Practicability+of+proton+therapy+using+compact+laser+systems.">Practicability of proton therapy using compact laser systems.</a> Medical Physics. 31 (6), 1587-1592 (2004).</li><li>Roth, M., 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=Laser-Driven+Neutron+Source+Based+on+the+Relativistic+Transparency+of+Solids.">Laser-Driven Neutron Source Based on the Relativistic Transparency of Solids.</a> Physical Review Letters. 110, 044802 (2013).</li><li>Noaman-Ul-Haq, M., 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=Statistical+analysis+of+laser+driven+protons+using+a+high-repetition-rate+tape+drive+target+system.">Statistical analysis of laser driven protons using a high-repetition-rate tape drive target system.</a> Physical Review Accelerators and Beams. 20 (4), 41301 (2017).</li><li>Li, Z., 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=Protons+and+electrons+generated+from+a+5-&#956;m+thick+copper+tape+target+irradiated+by+s-,+circularly-,+and+p-polarized+55-fs+laser+pulses.">Protons and electrons generated from a 5-&#956;m thick copper tape target irradiated by s-, circularly-, and p-polarized 55-fs laser pulses.</a> Physics Letters, Section A: General, Atomic and Solid State Physics. 369 (5-6), 483-487 (2007).</li><li>Shaw, B. 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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=Spectral+modification+of+laser-accelerated+proton+beams+by+self-generated+magnetic+fields+Related+content+New+Journal+of+Physics+Spectral+modification+of+laser-accelerated+proton+beams+by+self-generated+magnetic+fields.">Spectral modification of laser-accelerated proton beams by self-generated magnetic fields Related content New Journal of Physics Spectral modification of laser-accelerated proton beams by self-generated magnetic fields.</a> New Journal of Physics. 11 (15), 83018 (2009).</li><li>Treffert, F., 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=Design+and+implementation+of+a+Thomson+parabola+for+fluence+dependent+energy-loss+measurements+at+the+Neutralized+Drift+Compression+experiment.">Design and implementation of a Thomson parabola for fluence dependent energy-loss measurements at the Neutralized Drift Compression experiment.</a> Review of Scientific Instruments. 89 (10), 103302 (2018).</li><li>Pappalardo, A., Cosentino, L., Finocchiaro, P. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=An+imaging+technique+for+detection+and+absolute+calibration+of+scintillation+light.">An imaging technique for detection and absolute calibration of scintillation light.</a> Review of Scientific Instruments. 81 (3), 33308 (2010).</li></ol>

With some variations, the target fabrication process described in this protocol is common (e.g., Zaffino et al.23). Here, one unique step that is critical to the operation of automatic positioning is the addition of nanometer-scale roughening in ring-shaped areas on the back of the wafer (step 1.2.3). The purpose of this step is to increase the diffused scattering of light incident on the wafer in those areas. The ranging sensor shines a low-power laser beam on the wafer, collects the scattered li...

An erratum was issued for:&#160;<a href="https://www.jove.com/t/61056">Automated Delivery of Microfabricated Targets for Intense Laser Irradiation Experiments</a>. The author list was updated.
The author list was updated from:
Yonatan Gershuni1,2, Michal Elkind1,2, Itamar Cohen1,2, Aviad Tsabary1,2, Deep Sarkar1,2, Ishay Pomerantz1,2 
1The School of Physics and Astronomy, Tel Aviv University, 
2Tel Aviv University Center for Light-Matter Interaction
to:
Yonatan Gershuni1,2, Michal Elkind1,2, Dolev Roitman1,2, Itamar Cohen1,2, Aviad Tsabary1,2, Deep Sarkar1,2, Ishay Pomerantz1,2 
1The School of Physics and Astronomy, Tel Aviv University, 
2Tel Aviv University Center for Light-Matter Interaction

An erratum was issued for:&#160;<a href="https://www.jove.com/t/61056">Automated Delivery of Microfabricated Targets for Intense Laser Irradiation Experiments</a>. The author list was updated.

Erratum: Automated Delivery of Microfabricated Targets for Intense Laser Irradiation Experiments

High-intensity laser irradiation of solid targets generates multiple forms of radiation. One of these is the emission of energetic ions with energies at the Mega electron-volt (MeV) level1. A compact source of MeV ions has potential for many applications, such as proton fast-ignition2, proton radiography3, ion radiotherapy4, and neutron generation5.
A major challenge in making laser-ion acceleration practical is the ability to position micrometer-scale targets accurately within the focus of the laser at a high rate. Few target delivery technologies were developed to answer this challenge. Most common are target systems based on micrometer-scale thick tapes. These targets are simple to replenish and may be easily positioned within the focus of the laser. Tape target has been made using VHS6, copper7, Mylar, and Kapton8 tapes. The tape drive system typically consists of two motorized spools for winding and unwinding and two vertical pins placed between them to keep the tape in position9. The accuracy in positioning the tape surface is typically less than the Rayleigh range of the focusing beam. Another type of replenishable laser target is liquid sheets10. These targets are delivered rapidly to the interaction region and introduce a very low amount of debris. This system comprises a high-pressure syringe pump continuously supplied with liquid from a reservoir. Recently, novel cryogenic hydrogen jets11 were established as means to deliver ultrathin, low-debris, replenishable targets.
The main drawback of all of these replenishable target systems is the limited choice of target materials and geometries, which are dictated by mechanical requirements such as strength, viscosity, and melting temperature.
Here, a system able to bring micromachined targets to the focus of a high intensity laser at a rate of 0.2 Hz is described. Micromachining offers a wide choice of target materials in versatile geometries12. The target positioning is performed by a closed-loop feedback between a commercial displacement sensor and a motorized manipulator.
The target delivery system was tested using a high-contrast, 20 TW laser system that delivers 25 fs-long laser pulses with 500 mJ on target. A review of the laser system&#8217;s architecture is given in Porat et al.13, and a technical description of the target system is given in Gershuni et al.14. This paper presents a detailed method for making and using this type of system and shows representative results of laser-ion acceleration from ultrathin gold foil targets.
The Thomson Parabola ion spectrometer (TPIS)15,16 shown in Figure 1 was used to record the energy spectra of the emitted ions. In a TPIS, accelerated ions pass through parallel electric and magnetic fields, which places them on parabolic trajectories in the focal plane. The parabolic curvature depends on the ion&#8217;s charge-to-mass ratio, and the location along the trajectory is set by the ion&#8217;s energy.
A BAS-TR imaging plate (IP)17 positioned at the focal plane of the TPIS records the impinging ions. The IP is attached to a mechanical feedthrough to allow translation to a fresh area before each shot.

<table>
	<tbody>
		<tr>
			<td>76.2 x 127mm EFL 90&#176; Protected Gold 100&#197; Off-Axis Parabolic Mirror</td>
			<td>Edmund optics</td>
			<td>35-535</td>
			<td></td>
		</tr>
		<tr>
			<td>MicroTrak 3 LTS 120-20</td>
			<td>MTI Instruments</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Ultrafast high power dielectric mirrors for 800 nm</td>
			<td>Thorlabs</td>
			<td></td>
			<td></td>
		</tr>
	</tbody>
</table>

automated delivery of microfabricated targets for intense laser irradiation experiments

Described is an experimental procedure that enables high-power laser irradiation of microfabricated targets. Targets are brought to the laser focus by a closed feedback loop that operates between the target manipulator and a ranging sensor. The target fabrication process is explained in detail. Representative results of MeV-level proton beams generated by irradiation of 600 nm thick gold foils at a rate of 0.2 Hz are given. The method is compared with other replenishable target systems and the prospects of increasing the shot rates to above 10 Hz are discussed.

This target delivery system was employed to accelerate ions from the back side of 600 nm thick gold foils. When irradiated with a normalized laser intensity of a0 = 5.6, these ions were accelerated by the target normal sheath acceleration (TNSA) mechanism21. In TNSA, the lower-intensity light that preceded the main laser pulse ionized the front surface of the target foil. The ponderomotive force exerted by the main laser pulse drove hot electrons through the bulk matter. A charge separa...

Watch this Scientific Journal Video about Automated Delivery of Microfabricated Targets for Intense Laser Irradiation Experiments at JoVE.com

Automated Delivery of Microfabricated Targets for Intense Laser Irradiation Experiments

A protocol is presented for automated irradiation of thin gold foils with high intensity laser pulses. The protocol includes a step-by-step description of the micromachining target fabrication process and a detailed guide for how targets are brought to the laser&#39;s focus at a rate of 0.2 Hz.

Described is an experimental procedure that enables high-power laser irradiation of microfabricated targets. Targets are brought to the laser focus by a ...

Intense laser radiation experiments of submicrometer scale targets are currently performed at slow shot rates. Our protocol solved this challenge by placing these targets quickly at the focus of the laser in an automated manner. Our target system enables the collection of data incorporating a large number of laser shots with target parameters changed in small increments, as well as applications that benefit from a high overall radiation dose.Visual demonstration of this protocol will show the subtleties of the wafer fabrication process and target alignment. Demonstrating target fabrication process are process engineer Nirit Porecki Shamay and Nofar Livni. To fabricate the backside, use a 250 micrometer thick 100 millimeter diameter high stress silicon wafer in a one-zero-zero crystal formation coated on both sides with silicon nitride.Clean the wafer with acetone and with isopropanol. Then spin coat the wafer with HMDS resists to form an adhesive layer. Spin coat the wafer with an AZ 1518 positive photoresist.Bake the wafer at 100 degrees Celsius for one minute. Photolithograph 1, 000 by 1, 000 micrometer square openings under vacuum, exposing the wafer in one four to seven-second cycle to a 400 nanometer UV lamp so that the wafer is exposed to an overall fluence of 40 joules per centimeter squared. Then use an AZ 726 developer to expose the silicon nitride and a bath of dehydrated water to stop the process.Use a reactive ion etcher to remove the silicon nitride in the location of the squares. Place the wafer in an NMP bath for 20 minutes to remove the residual resist and photoresist, producing a replica of the mask on the silicon nitride layer. Then wash it under fresh water and let it dry.Sink the wafer in a 30%90 degrees Celsius potassium hydroxide solution to etch the silicon through the square openings. To fabricate the front side, repeat the previously described procedure with a mask shaped as three concentric rings. Use the reactive ion etcher to remove the silicon nitride where the rings are located, followed by an NMP bath to remove resist and photoresist leftovers.Roughen the silicon rings by sinking the wafer in nitric acid and in a solution of 0.02 molar silver nitrate and four molar hydrogen fluoride. On the etched side of the wafer, use a physical vapor deposition machine to sputter a layer of a few hundred nanometers of gold on top of a 10 nanometer film of adhesive titanium, nickel, or chrome. Block the beam and bring the first target into view under a high magnification microscope.Point a triangulation ranging sensor to the roughened ring closest to the target and record its displacement reading. Leaving the microscope in place, move the wafer away to clear the beam path. Use the two folding mirrors and the off-axis parabolic mirror to align the beam in low power into the field of view of the microscope.Adjust these three mirrors to correct astigmatisms in the beam. The result should be a nearly diffraction limited focal spot. Block the laser beam and bring the target back to the focus of the microscope.Then validate its position using the microscope and the ranging sensors reading. Use software to implement a closed loop feedback between the focal axis manipulator of the target and the displacement sensor reading using the previously recorded displacement value as the setpoint. Once the closed loop positioning has reached a desired tolerance distance from the setpoint, irradiate the target with a single high-power laser pulse.Record data from particle diagnostics and repeat the process with the next target brought into focus by the software. This target delivery system was employed to accelerate ions from the backside of 600 nanometer thick gold foils. A time series of the target displacement along the focal axis is shown here.The values are relative to the focal position setpoint. The green dots indicate when the target displacement was within a tolerance value of one micrometer from the setpoint, which is when a laser shot was taken. Thomson parabola ion spectrometer traces were obtained from 14 consecutive irradiations of 600 nanometer thick gold foil targets.Energy spectrums were derived from these traces. The peak-to-peak stability of the maximum proton energy was within 10%Following this procedure, investigations of ion and electron acceleration from solid foils neuron generation can be performed in a systematic manner.

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