Lead Body |
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| HLX Body | LNX Body |
Current lead bodies are available in two different basic geometries. The simpler LNX body geometry accommodates the superconducting wires in straight grooves. The HLX body geometry has a helical structure twisting through 120 degrees along the full length of the lead.
Each of these basic geometries is available in three forms. The ‘Solid’ form provides a rigid lead, this is useful when the two lead ends are contacted to components that need to be well mechanically coupled.
The ‘Tubular’ form remains rigid but the reduced amount of composite material in the lead cross section reduces the overall thermal conductance of the lead.
The ‘Flexible’ form of the lead has a slightly lower thermal conductance than the ‘Tubular’ form. In addition, the flexible lead has a small degree of compliance. This may be useful during installation when the end contacts are not perfectly aligned. This lead type has a lower degree of mechanical coupling between the two ends; this lead will therefore provide superior vibration isolation.
LNX Lead End |
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HLX Lead End |
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| Type A (M/E) | Type B: 1 hole | 2 hole | 3 hole |
Once the lead body type is selected each lead end may be selected. The requirements of lead ends will often be different when each end is stationed at a significantly different temperature and to accommodate this the two lead ends are identified as ‘warm’ and ‘cold’.
The Type A lead allows for a butt joint. This lead end is available in metric dimension (Type AM) and imperial dimension (Type AE). Each anchor hole is reinforced with a stainless steel helicoil; M6 for the metric lead end and ¼-20 for the Type AE lead.
This lead end has a through hole to allow for a holding torque when tightening the connecting bolt.
The Type B lead end allows for a lap joint. These ends are available with one, two or three anchor holes. Each hole has 6.6mm clearance diameter which will accommodate either a metric M6 bolt or an imperial ¼ -20 bolt.
The lead ends may be made from ETP grade copper, OFHC grade copper or high purity Niobium. The material properties are summarised on the Ordering and Pricing tab.
All lead ends are Nickel plated in order to pacify the surface.
High Current Cables
These cables are for use connecting power supplies to your system or for daisy-chaining multiple systems. These cables are not suitable for in-vacuum applications. The cables are PVC insulated and are intended for indoor use only. Leads are sold in pairs and are colour coded red and black.
The cables shown include voltage taps at one end which are useful for measuring or monitoring voltage drops either along the lead or across the energised device. Leads come with the choice of no taps, one end tapped or both ends tapped.
| Copper cross-section | Normal DC rating | Cool DC rating |
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| 16 mm2 | 150A | 50A |
| 25 mm2 | 300A | 100A |
| 35 mm2 | 400A | 120A |
| 50 mm2 | 500A | 150A |
Contact Shims
In order to make a good thermal and electrical connection between the lead ends and their anchor point a contact shim is recommended. Contact shims deform to ensure that the contact area between the lead end its anchor point is maximised. These are offered in 99.9% pure silver or 99.99% pure Indium, they are cut to size and are 0.005” thick. The electrical and thermal properties at room temperature are summarised here (note, these values will vary significantly at cryogenic temperatures):
| Metal | Thermal conductivity [W . m-1 . K-1) | Electrical resistivity (n Ω . m] |
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| Ag - Silver (99.9% pure) | 430 at room temperature | 16 at room temperature |
| In - Indium (99.99% pure) | 82 at room temperature | 80 at room temperature |
| Lead End | Contact Area | Shim | Clamp | |
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| Type A |  |
205mm2 one face only |
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P/N NT001TypeAShimAg – Silver
P/N NT001TypeAShimIn – Indium |
P/N NT001TypeAEClamp – Imerial ¼ “ x 20
P/N NT001TypeAMClamp – Metric M6 |
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| Type B1 |  |
487mm2 one face 974mm2 two faces |
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P/N NT001TypeB1ShimAg – Silver
P/N NT001TypeB1ShimIn – Indium |
P/N NT001TypeB1Clamp | |||
| Type B2 |  |
886mm2 one face 1772mm2 two faces |
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P/N NT001TypeB2ShimAg – Silver
P/N NT001TypeB2ShimIn – Indium |
P/N NT001TypeB2Clamp | |||
| Type B3 |  |
1285mm2 one face 2570mm2 two faces |
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P/N NT001TypeB3ShimAg – Silver
P/N NT001TypeB3ShimIn – Indium |
P/N NT001TypeB3Clamp | |||
Compression plate assembly
Compression plates are provided to enable good compression of the contact shims. The lead ends are made from Nickel plated copper (101 grade, OFHC). This copper grade is very pure and results in a relatively soft material. The compression plates are made from 5mm stainless steel and allow for a higher and more even compression than simply using bolts. Belleville washers are also used to ensure that pressure remains applied to the contact after contraction due to cooling.
The A type lead end has a helicoil insert and hence only a single compression plate is provided for this lead end.