Weaving the search for dark matter

there's been evidence for several decades that there is mass in the

universe that we haven't been able to account for

--you can't see it directly with telescopes

it doesn't like to interact with light

you can't reflect light off of it

it doesn't really like to emit light but in spite of that it does seem

to have mass and does seem to gravitationally influence other things

in distant galaxies

we haven't detected it in the direct sense

and that's what LZ is trying to do

Hi i'm Knut Skarpaas, the 8th and that's

Knut Skarpaas, the ninth,

Knut Skarpaas the seventh was actually possibly the first

engineer at SLAC

so there was some interest in making some grids for LZ

the grids were very large

I was suggesting that we put weights on every wire to get nice tension

--the only way to do that I figured was to make a loom so I started

looking at looms and things from my childhood like these things from my

mother back when I was a little kid we used to do little crafting things and I

was looking at how they made badminton rackets and then I started studying like

Navajo women weaving...weaving from Egyptian times, some Scottish and Irish

weaving all kinds of different ways to make thread interact

then I basically took these techniques and mixed them

with my CAD

to make the geometries perfect

and made a system where I could actually have a factory

that would create metal cloth under tension that would move on rails and it

would just leave this path of tension cloth behind it

my name is Rachel Mannino

and I'm a postdoc on the LZ experiment

--my name is Ryan Linehan I'm a graduate student

When we're getting ready to build a grid, the first thing we do is we get the

loom ready right so we make sure everything's clean

the loom is in a class 100 clean room

you set up two different directions of wires so first

you set all the wires that go in one direction called the warp direction

then you start weaving in the second direction

and the way the heddles work

is it'll take like the say odd numbered wires

bring them up and the even-numbered wires go down

and then you just kind of drive a wire through that opening

then once you actuate the heddles you

can flip them and capture that wire in place and you just kind of repeat that

just before gluing, there's kind of a small step that is important for a

certain set of grids called alignment we need to get a giant ring positioned

correctly to at max about two times the width of a human hair

now the gluing is another very difficult part we bring this this ring up

underneath the mesh we push it up against the mesh to ensure contact

between the wires and the ring and then we lay down a bead of glue

-with a robot, nonetheless

the way we do that is with a giant 3D printer that spits glue

out and kind of orbits around the ring several times to extrude

all the glue that we need

--fun facts is that this robot flies about 200 microns above the

surface of the wires and and extrudes glue that close when you have the glue

down you take another ring and you put it on top of that glue so you basically

sandwich the wires in between two rings and wait until the glue is dry then you

have your grid and you can cut the grid out from the mesh and everyone

celebrates because we've successfully completed a grid --yeah!

there's this balance

between your structural stability --your mechanical stability and then also

making sure that it'll perform the way you want it to perform

a problem with the scale of LZ

is that it's so big that if you have a parallel wire you can get

some deflection and your wires gonna sag in the center and we don't want that

because you want really uniform electric fields in our detector

other design considerations are

you want to make sure that your photomultiplier tubes at the

top of the detector which are actually detecting your signal, right

they're seeing the light from these collisions

and your xenon you want to make sure that they're

not going to be blocked by the wires themselves

so you want to make sure that your opacity

is really low that light can get through the mesh so

that kind of helps determine the wire diameter

so a lot of different design considerations

they do have commercial meshes available

but not in the size we wanted so once

people decided that they wanted a mesh they had to make it themselves or change

the scope of the detector and they didn't want to make the detector smaller

because that would make it less sensitive

(this is the first real one, that's going to actually go in the detector)

we will box them up and ship them out to South Dakota to SURF

which is the Sanford Underground Research Facility in Lead, South Dakota

it's there that they will be assembled

into LZ and will be kind of bottled up

and put underground into a mine

where it will then be turned on in the coming months

[SLAC logo & music]

 Farrin Abbott/SLAC National Accelerator Laboratory