AMS-02 Cryosystem

AMS-02 Cryosystem

Phase III Flight Safety ReviewJanuary 12, 2010

Phil Mott

AMS-02 Cryosystem

Vacuum Case Main Helium Tank Plumbing & Valves

Cryosystem Schematic

Vacuum Case

Vacuum jacket for the superconducting magnet

Inner Joint:– Welded U groove design

Outer Joint:– Bolted joint with double o-rings

SUPERFLUID HELIUM TANK

MAGNET RACETRACK

COIL(DIPOLE COIL ROTATED 90o)

VACUUM SPACE1 x 10-6 TORR

SUPER INSULATION &

VAPOR COOLED SHIELDS

SUPER INSULATION &

VAPOR COOLED SHIELDS

UPPER CONICAL FLANGE

UPPER SUPPORT RING

OUTER CYLINDER

INNER CYLINDER

OUTER JOINT

INNER JOINT

LOWER SUPPORT RING

LOWER CONICAL FLANGE

Vacuum Case Certification

Helium Leak Tests– Both o-rings at all locations and both

closeout welds were leak tested to show a better than 1.0 x 10-7 std cc/sec permeation

Proof Pressure Test:– The VC was successfully pressure

tested to 1.8 atm absolute (1.0 x MDP) Closeout Weld

– Process certified to MSFC-SPEC-504C– Inspections

VisualDye PenetrantUltrasonic

Main Helium Tank

2500 liter toroidal vessel which is constructed from Al 5083– All welded structure

Helium Leak Test– Both halves leak tested along

with full assembly Proof Pressure Test

– Successfully tested to 3.3 bar (MDP is 3.0)

Superfluid Helium Leak Test– Tank was leak checked after it

was assembled inside of the VC due to issues with the ground testing rig. No leaks were found.

Burst Discs

Both the Vacuum Case and the main helium tank are protected by burst disc. These will be covered in detail in a later presentation.

Warm & Cold Valves

The system uses two sets of gas-actuated valves in order to move the liquid helium around the cryosystem.– The cold valves are

located on the main helium tank

– The warm valves are located on the VC

Actuation gas comes from the Warm Helium Supply on the VC.

Pilot Valve Vacuum Vessel (PVVV)

The PVVV contains the pilot valves that control the cold valves inside of the magnet. This prevents heat leak into the actuation lines.

System was installed in place, so a proof pressure test to 1.5xMDP cannot be done without risking damage to other components. Equivalent verifications being developed with EP.

Vacuum leak checked.

PVVV Changes

Design changed from an all welded configuration to a bolted o-ring seal (for valve replacement if necessary). Does not affect safety.

Line added to vent pump from PVVV to pump out helium from valve exhaust for a reduced heat load from L-88 to launch.

Warm Helium Supply

Provides helium that actuate both the warm and cold valves.

Covered in detail in a later presentation

Superfluid Cooling Loop (SCL)

The SCL is a closed system that is used to continually cool the magnet.

A serpentine tube is located inside of the main helium tank and the cooling loop is run along the top and bottom of the magnet coils.

The SCL is protected by a 20 bar burst disc that vents into the main helium tank.

Nominal operating pressure is 1 bar

Cool Down Circuit

Only used to initially cool down the magnet and after a quench to re-cool the magnet.

Tubes run along the top and bottom of the magnet coils and connected by thermal bus bars.

Current Leads

The current leads are used to charge the magnet and are cooled by flowing helium through the middle of the lead.

The current leads functioned nominally after the fix was implemented (covered in a separate presentation).

Thermo-mechanical Pump

The thermo-mechanical pump is used to pump helium from the main tank into the cryosystem during re-cooling of the magnet after a quench and during charging.

It has no moving parts and is actuated by a heater and primed by surface tension.

Both TMP’s function as designed.

Porous Plug & Nominal Venting

As helium in the main tank boils off, it is vented through a porous plug that separates the gas from the superfluid helium.

The vapor passes through the Vapor Cooled Shields, and then out through a port on the VC which then splits into three lines.– The first line goes to the flight vent,

which is used on-orbit– The second line goes to a port with a

connection to the CGSE pumps, which is used on the ground.

– The third line goes to the On-Board Pump, which is used during transportation and in the payload bay.

Vapor Cooled Shields (VCS)

There are 4 VCS between the helium tank and the VC. As the helium boils off in the main helium tank, it flows through pipework attached to the 4 VCS’s that intercept incoming heat.

The VCS’s are constructed from strips of pure aluminum.

The VCS’s are separated by layers of superinsulation (aluminized Mylar and nylon netting)

VCS Supports

VCS 2 & 4 are supported by a carbon fiber honeycomb structure on the top and bottom. They are connected to each other by a series of wires.

Cryocoolers

Four Stirling-cycle cryocoolers used to remove additional heat from VCS 4 and reduce the external heat leak.

The cryocoolers were developed by Sunpower and modified by GSFC for flight.

Qualification cooler has been run for twice the nominal mission lifetime without incident.

Fill Port

The Fill Port is only used for ground operations during filling and topping off of the main helium tank.

AMS-02 Cryosystem

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