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<!DOCTYPE html>
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<title>Dust Accelerators</title>
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<div class="bottom__nav"><a href="index.html">Home </a><span class='divide'> ❱ </span><span class="bottom__nav__page"> Facilites</span></div>
<div class="page__title">Dust Accelerators</div>
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<h2>IMPACT Dust Accelerators</h2>
<nav>
<ul>
<li><a href="#dal">Dust Accelerator Laboratory (DAL)</a></li>
<ul>
<li><a href="#targets">Target Chambers</a></li>
<ul>
<li><a href="#leil">Large Experimental (LEIL) Chamber</a></li>
<li><a href="#uhv">Utra High Vacuum (UHV) Chamber</a></li>
<li><a href="#ice">Ice Target Chamber</a></li>
<li><a href="#gas">Gas Target Chamber</a></li>
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<li><a href="small_acc">Small Dust Accelerator</a></li>
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<div class="three_quarter">
<section class="clear">
<a name="dal"></a>
<h1><b>Dust Accelerator Laboratory (DAL)</b></h1>
<p>The Institute for Modeling Plasma, Atmospheres, and Cosmic Dust (IMPACT) houses a 3 MV linear electrostatic dust accelerator which is used for a variety of impact research activities as well as calibrating dust instruments for space applications. The dust accelerator is equipped with a 3 MV Pelletron generator capable of accelerating micron and submicron particles of various materials to velocities approaching 100 km/s.</p>
<p>The dust accelerator is available for use by outside groups, following approval from the Colorado accelerator team. To apply for accelerator beam time and to discuss usage costs, please fill out the application form (available below) and send it to one of the following contact personnel:</p>
</section>
<section class="one_half first">
Prof. Tobin Munsat<br />
390 UCB<br />
Boulder CO, 80309<br />
<a href="mailto:tobin.munsat@colorado.edu">tobin.munsat@colorado.edu</a>
</section>
<section class="on_half">
Prof. Mihály Horányi<br />
390 UCB<br />
Boulder CO, 80309<br />
<a href="mailto:mihaly.horanyi@colorado.edu">mihaly.horanyi@lasp.colorado.edu</a>
</section>
<section class="clear">
<p>The application form can be found <a href="acc_info/BeamTimeApplication.pdf" target="_blank">here</a>.</p>
<p>A PDF containing accelerator information can be found <a href="acc_info/DustAcceleratorInfoSheet.pdf" target="_blank">here</a>.</p>
<p>The current accelerator schedule can be found <a href=" https://calendar.google.com/calendar/embed?src=munsat%40colorado.edu" target="_blank">here</a>. Note that while we try to keep this up to date, things change regularly. Please contact <a href="mailto:tobin.munsat@colorado.edu">Tobin Munsat</a> for the most up to date information especially for booking times.</p>
</section>
<section class="clear">
<h1><b>DAL description</b></h1>
<p>The figure below illustrates the operation principle: the dust source is mounted onto the HV terminal of the Pelletron and individual charged dust particles are accelerated by the electrostatic field. A pair of pickup tube detectors is used to measure the velocity of each particle and the logic circuit of the Particle Selection Unit (PSU) selects the particles within a desired range of velocity and charge. The rest of the particles are deflected and do not reach the experimental chamber.</p>
<figure><img loading="lazy" src="images/ACC_diagram.png" alt="Dust Accelerator" /></figure>
<p>The entire system is oil-free and can be pumped down to the low 10-7 Torr range using a combination of turbomolecular pumps and cryopumps. All turbomolecular pumps are magnetically levitated to reduce vibrations, and all high-vacuum pumps are backed with oil-free forepumps. The laboratory also houses a separate, 20 kV "mini-accelerator" used to test various dust sources before installation into the main accelerator.</p>
</section>
<section class="clear">
<h2>Dust size and velocity distribution</h2>
<section class="one_third first">Dust particles with diameters ranging from 0.03 - 2 µm have been accelerated to velocities of 0.5 - 115 km/s. A detailed map of the distribution of launched dust particles is shown in the figure to the right.</section>
<section class="two_third">
<figure><img loading="lazy" src="images/ejected_dist_3.png" alt="Dust Accelerator" />
</figure>
</section>
<section class="clear">
<h2>Selection capability</h2>
<p>An FPGA-based unit performs two functions, using the pickup-detector signals as inputs. First, it digitally filters the raw signals to detect particles with extremely low charge levels (on the order of 4000 electrons) within the background detector noise. Secondly, it acts as a "particle selection unit", which downselects a user-selectable sub-population of the launched dust. Users can downselect based on particle velocity, charge, or mass.</p>
</section>
<section class="clear">
<h2>Dust Rates and beam size</h2>
<p>The rate of particles reaching the target is highly dependent on the downselection criteria used. The rate of particles with no downselection is typically between 0.5 and 1 per second. If, for example, particles are velocity-limited to ≥10 km/s, the rate goes down to around 5-10 per minute. Higher velocity thresholds or additional selection criteria reduce the rates further.</p>
<p>The shape of the dust beam is typically Gaussian with a characteristic width of ~6 mm.</p>
</section>
<section class="clear">
<h2>Available materials</h2>
<p>The most common material in use at the accelerator is spherical iron particles, ranging in size from ~30 nm - 2 µm in diameter, and subsequently downselected as needed by the particle selection unit. Additional spherical metallic materials can also be used, though only a small variety have been tested so far. (It is expected that any spherical metallic particle can be launched, but they must be tested in the mini-accelerator before use).</p>
<p>Insulating particles such as silicates (olivine, SiO<sub>2</sub>, etc.) which have been coated with a very thin layer of platinum or conductive polymer (polypyrrole) can also be used, though use of coated silicates is typically reserved for more specialized applications.</p>
</section>
<section class="clear">
<h2>Data acquisition details</h2>
<p>Waveforms from each of the three pickup tube detectors are recorded with a 12-bit NI PXI-5124 unit running at 10-100 MSamp/s.</p>
<p>User data is recorded on either a LeCroy Waverunner 104Xi-A oscilloscope (4 channels, 12-bit, 5 GSamp/s 1 GHz bandwidth) or an NI PXI-5124 unit (2 channels, 12-bit 200 MSamp/s combined). Users may of course augment the DAQ systems as needed.</p>
</section>
<section class="clear">
<h2>Data "package" provided to user</h2>
<p>At the conclusion of an experimental run, users are provided with a data "package" which contains data on the launched particles, as follows:</p>
<ul>
<li>CSV file; contains "metadata" on each particle: timestamp (ms resolution), velocity, mass, charge, radius.</li>
<li>HDF5 file; contains all of the above, in addition to the waveforms recorded by all NI units (i.e. all raw pickup-detector waveforms plus user data from the PXI-5124 unit).</li>
<li>LeCroy files; contain all user waveforms recorded by the LeCroy 104Xi-A oscilloscope.</li>
</ul>
</section>
<section class="clear">
<a name="targets"> </a>
<h2><b>Target Chambers</b></h2>
<p>IMPACT hosts a variety of target chambers that can be mounted at the end of the beam line.</p>
</section>
<section class="clear">
<a name="leil"></a>
<h3>Large Experimental (LEIL) Chamber</h3>
<p>The LEIL chamber is 1.22 m in diameter, 1.52 m long, and has a volume of 2 m<sup>3</sup>. An externally-controlled moving translation stage is installed in the chamber which allows control over the impact position in one dimensions (transverse to the beam line) without breaking vacuum. All ports are standard conflat, of various sizes, and a variety of different viewports and electrical feedthroughs are available.</p>
<figure><img loading="lazy" src="images/leil_new.png" alt="LEIL Chamber"/>
<figcaption>The large experimental chamber (LEIL) mounted at the end of the beam line.</figcaption>
</figure>
</section>
<section class="clear">
<a name="uhv"></a>
<h3>Ultra High Vacuum (UHV) Chamber</h3>
<p>IMPACT operates a dedicated chamber designed for experiments requiring ultra-high vacuum conditions (UHV). Equipped with a cryopump and baking system, this chamber can be directly connected to the accelerator and routinely reaches conditions in the 10^-10 torr range, with a demonstrated base pressure to date of 2 x 10^-10 torr. This chamber is appropriate for impact experiments requiring very clean conditions, exceptionally low background gas pressure, or both. To date it has been used to investigate neutral species released from hypervelocity dust impact.</p>
<p>The chamber is unusually large for a UHV system; the usable interior volume forms a cylinder approximately 60 cm in diameter by 70 cm tall. Mounting tabs are provided for large or heavy experiments. Large (8″ CF) flanges are provided for directly-mounted experiments or windows. Experiments requiring access to the lowest pressures in this system should be able to withstand at least a 100 C bakeout temperature. </p>
<figure><img loading="lazy" src="images/uhv_chamber.jpg" alt="Ultra High Vacuum Chamber"/>
<figcaption>The Ultra High Vacuum (UHV) Chamber</figcaption>
</figure>
</section>
<section class="clear">
<a name="ice"></a>
<h3>Ice Target Chamber</h3>
<p>The ice target chamber is designed for growing and maintaining ice targets in vacuum. The chamber can be easily moved and hooked to the dust accelerator. The ice target has an ice thickness monitoring system, a rotational stage for the ice system, and a linear time of flight mass spectrometer. The temperature of the ice mount can be varied down to 80K.</p>
<figure><img loading="lazy" src="images/ice_chamber.jpg" alt="Ice Target Chamber"/>
<figcaption>Students <a href="people.html#goode">Bill Goode</a> (left) and <a href="people.html#nelson">Oak Nelson</a> (in back) work on the assembly of the laser measurement system for the ice target vacuum chamber with <a href="people.html#dee">Dr. Richard Dee</a> looking on.</figcaption>
</figure>
<br />
<section class="one_half first">
<figure><img loading="lazy" src="images/ice_chamber2.png" alt="Ice Target Chamber"/>
<figcaption>Ice target vacuum chamber CAD model showing cryogen feed, copper ice target backing plate (bottom) and dust accelerator beam line (from left).</figcaption>
</figure>
<p></p>
</section>
<section class="one_half">
<figure><img loading="lazy" src="images/ice_target2.png" alt="Ice Target"/>
<figcaption>View of the prototype cryogenic ice target (left port in image) at a temperature of 80K in vacuum.</figcaption>
</figure>
<p></p>
</section>
</section>
<section class="clear">
<a name="gas"></a>
<h3>Gas Target Chamber</h3>
<p>The dust ablation chamber simulates micrometeoroids ablating in atmospheric gases. Gas pressures ranges from 0.02-0.5 mTorr in the ablation chamber and can be controlled with 0.1 mTorr accuracy. A variety of gases such as (e.g. N2, O2, air, He, etc…) can be used to simulate micrometeoroid ablation into Earth or other atmospheres.</p>
<figure><img loading="lazy" src="images/gas_chamber.jpg" alt="Gas Target Chamber"/>
<figcaption>Student <a href="people.html#thomas">Evan Thomas</a> plugging in one of the PMT detectors before a test run. Pictured above is a 3D cutaway render of the ablation chamber.</figcaption>
</figure>
</section>
<section class="clear">
<a name="small_acc"></a>
<h2><b>Small Dust Accelerator</b></h2>
<section class="clear"><p>The small dust accelerator is used for a wide array of experiments and for characterizing dust properties before being loaded into the large accelerator. Using the same principles as the large accelerator, dust is picked up by two detectors allowing us to analyze mass, speed, and charge of the particles. Without a pelletron, the small accelerator is capable of providing 20kV acceleration voltages. Ease of accessibility compared to the large accelerator allows for quick dust source changes, resulting in studies of multiple types of dust.</p> </section>
<figure><img loading="lazy" src="images/small_acc.jpg" alt="Small Accelerator"/>
<figcaption>Student <a href="people.html#fontanese">John Fontanese</a> working on the small accelerator.</figcaption>
</figure>
</section>
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