Notes from DM-Ice Technical Meeting

Participants: Reina, Jeff, Karsten

Actions items are shown in blue.

Location of Detector

-DM-Ice would be deployed along with strings 79 and 80

-Darren Grants’ preliminary simulations indicate that a depth of about 2000m would be better than the bottom of the IceCube array. Rejection of muons is higher.

-We don’t know where the cable breakouts are. Have all cable breakouts been already fabricated? Are cables at pole?

> Reina to find out location and status of cable breakouts. This will determine the vertical location of the DM-Ice detector package.

Housing and Pressure Vessel

-Default proposal is to enclose NaI crystals in titanium cylinder. About 6” ID and 1” wall thickness. About 80-100cm long. Design of vessel similar to cylinders of radio experiment. Same flange design. DM-Ice detector would have flanges at top and bottom to access PMTs from both sides.

-Main electronics board would be outside the detector cylinder and be housed in DOM. Can we use penetrators from SeaCon to make connection between DOM and DM-Ice detector cylinder?

-What cables are used in the SeaCon penetrators of the radio experiment? Can we use the same design to bring out PMT signal from cylinder to DOM?

-DM-Ice detector cylinder would contain 2 PMTs. Will need 2 cable penetrators to connect DM-ice detector cylinder to DOM with main board. HV for PMTs has to be generated from separate board inside the DM-ice detector cylinder.

-Cylinder with detectors would be taped to cable.

> Jeff will sketch up conceptual layout of DM-Ice detector cylinder with cable

breakouts, DOM, and connection to IceCube cable. Inlcude estimate of dimensions

and wall thickness of vessel based on mechanical data for pure titanium

-Looked at NAIAD technical detector paper. Will use Spooner’s detector as baseline package to design deployment vessel. In fact we may want to be able to mount and run Spooner’s detectors :as-is” inside this deployment vessel.

-Some open questions:

  • What material should we use for light guides: silica, acrylic, mineral oil?
  • What is length of PMTs used in NAIAD detector?
  • How is detector package mounted? Can make support structure inside cylinder out of acrylic.
  • Should we backfill cylinder with mineral oil as was done in NAIAD?

Karsten and Reina to look at above issues.

Radioactivity

-Phone call with Tom Shutt from Case Western. LUX has measured radioactivity of titanium. Pure titanium, not alloy, seems clean. Al Smith at LBNL finds limits on U, Th of < 0.02 ppb in U, Th of CP-1 titanium.

-LUX uses low-backgroud titanium for cryostat vessel. Fabricated by Ability in Chicago. Other company LUX talk with is Myer’s Tools near Chicago.

-LUX collaboration may have some titanium sheets that we could buy from them. Tom Shutt will ask colleagues.

> can use LUX numbers for backgrounds in titanium for simulation

-the other closest parts to NaI detectors would be

  • IceCube cable
  • HV board
  • SeaCon penetrators

> Reina to check if spare parts are available at PSL that we could radioassay at LBNL

PMTs

-LUX is developing a 3” low-background PMT with Hamamatsu based on R87-78. Currently 2” PMT is used. Tom Shutt offered to help with contact if we wanted to get these PMTs.

Electronics

-Main IceCube board will be in dedicated DOM outside DM-Ice cylinder. Plan to capture PMT signal with main IceCube board. Do we need all the other boards?

-Can HV Board be separated?

-How can we mount board inside DOM without PMT?

-For DM-Ice we need to have a HV Board inside detector cylinder close to PMTs. Cannot run HV through cable from DOM to detector cylinder.

-May need to include pure copper plates to shield background from HV board from NaI crystals.

> Reina, Karsten to understand DOM board and electronics configuration and draw up cabling scheme.

Integration

> based on current conceptual design develop list of all parts

scribe: K. Heeger