Beam Spot

Hi Everyone,

Got to see an actual spark inside the Pelletron, what you
see are the grid lines from the Dust Coordinate Sensor

The beam spot as seen from an astronomy camera
inserted into the middle of the beamline

Sorry for the long time between posts.  I'm trying to whip everyone in shape so they'll start blogging as well.  A couple of really exciting things have happened since my last post.  I've been working on determining why our accelerator speeds have only been up to about 10 km/s.  In order to answer this question, I've been using a CCD camera typically used for taking long exposures of the night sky and putting into the path of the beamline before our detectors.  Letting the dust hit a quartz target directly in front of this camera allows you to take images of the beam profile.  With this we were able to figure out where the beam was pointed, what it looked like, and most importantly, how to point it in the direction we want to point it in.

We were able to determine that at our current running parameters, the beam's best focus creates a spot size of about 2 mm.  By moving the back of the Pelletron we are able to steer the beam.  Using a laser attached to the Pelletron we can steer the beam to very high accuracy.  I was able to move the beam almost exactly 2 mm to the right and 3 mm down in that picture.  With this capability we made sure the beam was pointed through the detectors and then starting taking data.  The result of all that work?  We know see particles up to about 45 km/s!

Shu

Beam Profile

The focused spot of the beam profile.  The Einzel focusing
lens will focus particles with a specific charge-to-mass ratio
into a beam as seen 

Hi Everyone,

The halo of the beam profile.  Due to the non-constant
charging process in the source, the charge-to-mass ratio of
each particle can vary greatly.  This leads to this unfocused
halo around the focused spot.

We're still working hard over here at CCLDAS so unfortunately we've been neglecting the blog a little bit.  Some updated info on the accelerator, we've finally got a preliminary image of what the beam actually looks like going down the accelerator.  We put a window and foil as close to the source of the accelerator as we could and we ended up with these images of that foil.  Unfortunately, as you can see, our beam is pretty defocused right now.  Luckily we do expect a central beam plus a diffuse halo around it, which is what we see.  The only problem is that we want that central beam to be more like 1mm than 15, so we've got a bit of work to do.

The reason for the central beam and the halo has to do with the way the dust source works.  This particular source does not charge every particle the same, so the charge-to-mass ratio is not constant across all the particles.  The focusing of the beam on the other hand, is dependent on the charge-to-mass ratio.  What we would expect is that a majority of the particles will be charged to the same  charge-to-mass ratio, giving you a well focused central beam, but then the rest of the particles will end up in the diffuse halo around the central focus.

I'll be continuing these studies into next week and hopefully will have more updates for you by then.

Shu

DPS ready for dust testing

The dust position sensor (DPS) is finished and ready to give the position of its first dust particles during a test run in the small accelerator tomorrow. Similar to the dust trajectory sensor (DTS), DPS reads the pulses from induced charges on a grid of wires as a charged particle flies through. Comparing the pulses from each wire allows us to pinpoint the position of the particle. Unlike the DTS, the DPS is small enough to fit inside the beamline and can be placed in a number of locations.

LDEX flight model is here!!

Exciting news, our first piece of flight hardware is now being calibrated in our dust accelerator. This gives us some serious clout in the dust and space community! A week or two ago we shot dust at the engineering model, which was cool, but this is the real deal! Sorry for the poor picture quality, there wasn't enough light.

Hi Everyone,
I've been meaning to create a YouTube account for the lab for a while now and finally got around to it.  This is a time lapse I made using images captured from the dustcam while we were building the accelerator.  Whenever we get cool videos we'll be sure to post them to our account, TheCCLDAS.  Hope you guys like it!
Shu

LDEX in CCLDAS Accelerator

Hi Everyone,

LDEX in LEIL

David James and Keith Drake putting
LDEX into LEIL

It's been a while.  I'll try to make sure we get more regular updates.  In the meantime, something exciting happened recently, we have LDEX inside the LEIL target chamber and we were firing on it this past weekend (ugh yup, grad students don't get vacation...).  They're still doing some tests on it while it's under vacuum, but will hopefully be done sometime this week.

LEIL under vacuum with the laser
shining onto it

The good news though is that the particle selection unit seems to be doing its job in selecting particles.  We discovered, however, a bunch of particles still made it to LDEX despite the fact that they did not appear on our detectors.

For those who don't know, LDEX is the Lunar Dust EXperiment that will be flying aboard the Lunar Atmosphere and Dusty Environment Explorer (LADEE) mission in 2013.  It can measure the charge and mass of dust particles and will hopefully enlighten us on the density of dusty plasma in the terminator regions of the moon.

Shu

More SEM Images

Hi Everyone,

Here are some more cool SEM images of glass samples that we fired at.  As you can see we've got some larger structure around the micron crater.  Also, previous to this, I had only been able to find 3um craters which I thought was odd.  I have now found craters on the submicron scale.  These guys are really tough to find and image.  I'll hopefully have more images and a couple more details on them in the near future.

Shu

Small crater <1um.  These guys are really tough to image.

SEM image of dust damage on glass.  Crater is about 2 um.