3 He Fridge SPIRE WE Review Dec. 6-7, IFSI 1 3 He Sorption Fridge “Cooler” WE Preliminary Design Presented by: L. Rodriguez / CEA/SAp. Subsystem Analysis WE Design Development Plan

3 He Fridge SPIRE WE Review Dec. 6-7, IFSI 2 Subsystem Definition The Cooler Subsystem comprises * A 3 He evaporator thermally coupled to the focal planes * A sorption pump made of active charcoal to reach very high pumping speed allowing focal plane temperatures lower than 300 mK. * Gas heat switches to connect different parts of the subsystem to the superfluid Helium Tank during recycling and control the focal plane temperature during operations. * Calibrated temperature probes to allow fine control of the focal planes. * A thermal filter (TBC) between the fridge and the focal planes. The main functions to be handled are * Recycle the fridge to reach a focal plane temperature around 300 mK. * Provide a temperature regulation better than 2 mK (TBD) at the focal plane level Subsystem Analysis

3 He Fridge SPIRE WE Review Dec. 6-7, IFSI 3 Subsystem Requirements Subsystem Analysis

3 He Fridge SPIRE WE Review Dec. 6-7, IFSI 4 Subsystem Block Diagram Subsystem Analysis 300 mK 1.5 K 100 K 300 K

3 He Fridge SPIRE WE Review Dec. 6-7, IFSI 5 WE Subsystem Functional & I/Fs Subsystem Analysis Electrical I/F: The Thermal switches are operated by 0->200 µW analogue outputs. Coarse FP regulation will be assumed by proportional output on switch B. Fine regulation (± 2 mK) can be done by a resistor on each focal plane. Electrical I/F: Thermometer bias: 100nA 270mK: 50E3 Ω Dissipated power 0.5 nW Thermal & mechanical I/F: The cold tip is thermally linked to the focal plane arrays by large conductive bars. Thermal & mechanical I/F: The sorption pump is linked to the liquid helium tank by large conductive bars. Thermal & mechanical I/F: The fridge is attached to the 4K stage..

3 He Fridge SPIRE WE Review Dec. 6-7, IFSI 6 WE Subsystem I/Fs Subsystem Analysis

3 He Fridge SPIRE WE Review Dec. 6-7, IFSI 7 Failure & Criticality Analysis Subsystem Analysis

3 He Fridge SPIRE WE Review Dec. 6-7, IFSI 8 States of the Subsystem (1) Subsystem Analysis

3 He Fridge SPIRE WE Review Dec. 6-7, IFSI 9 States of the Subsystem (2) Subsystem Analysis STATE (I): 300 K. The 300 K state is only pertinent during ground operation. No direct action can be done at the subsystem level. Heater = offSwitch A = off Switch B = off Remark: If we use 3 He gas conduction switches, switches are open only at low temperature (below 10 K) STATE (II) -2 K IDLE. This standby mode is the standard mode when SPIRE is not operational. Only one action can be done from this state by the subsystem: recycling. Heater = offSwitch A = off Switch B = off STATE (III): RECYCLING. Recycling is one of the most complex state for the subsystem: this state can be reached from two starting points (II) & (IV), and access, in normal operations to the state (IV). The cooler subsystem can be recycled from the state (IV) to ensure sufficient autonomy at 300 mK even if the focal planes are already at cold temperature. The algorithm is presented hereafter. Default state: temperature out of range --> state II

3 He Fridge SPIRE WE Review Dec. 6-7, IFSI 10 States of the Subsystem (3) Subsystem Analysis STATE (IV): 0.3 K UNREGULATED. After recycling without active regulation the focal plane temperature evolves below 300 mK. The final temperature depends on the thermal load and the pumping speed of the charcoal pump. Now the pumping speed itself evolves with time, during the cold stage cycle modifying at slow rate the focal plane temperature. If measurements must be performed in this state in a degraded mode, no science loss will happen if we are able to perform de-correlation against blind pixels. Remark: The transition from the state (IV) to (II) is made without any action at the subsystem level. Heater = offSwitch A = off Switch B = on Default state: temperature out of range --> state II STATE (V): 0.3 K REGULATED. When temperature regulation is active, the electronic subsystem is able to maintain the focal plane temperature within 2 mK (TBC) for a long time. The most elegant way to perform the temperature regulation is to control the pumping speed by action on the charcoal pump. The adsorption process on charcoal is an exothermal reaction (source), the pump temperature can, then, be controlled by applying a variable thermal leakage in place of the "two states" switch (B). A fine regulation on each focal plane level (limited to few pW) can be done by an electrical heater with a larger bandpass (10 Hz-TBC) than those obtained by acting on switches modulation. Remark: The use of gas 3 He switches allows to have, here, a variable thermal conductance, driven by an analogue electrical command. Heater = offSwitch A = off Switch B = variable Default state: temperature out of range --> state IV (stop regulation)

3 He Fridge SPIRE WE Review Dec. 6-7, IFSI 11 Specific Subsystem Functions: Recycling Subsystem Analysis From state IVFrom state II STATE III

3 He Fridge SPIRE WE Review Dec. 6-7, IFSI 12 Specific Subsystem Functions: Temperature regulation Subsystem Analysis

3 He Fridge SPIRE WE Review Dec. 6-7, IFSI 13 Subsystem Parameters Subsystem Analysis The setting parameters: Focal plane temperature (set in operation) Switches:Maximum output voltages PID gains:set of 3 parameters (set in operation) Recycling times (Time1, Time2,…) (set in operation). The Subsystem H/K. †he thermometer calibration

3 He Fridge SPIRE WE Review Dec. 6-7, IFSI 14 WE implementation Telecommands The cooler subsystem sequences are “frozen” during the implementation of the flight model development.Only adjustments of the time sequences and gains will be necessary. S/W Implementation Recycling sequences and temperature regulation will be implemented in the master controller program. Dedicated electronics. There is no dedicated electronics. Subsystem Analysis

3 He Fridge SPIRE WE Review Dec. 6-7, IFSI 15 Overall description & Specification of the Subsystem dedicated electronics WE Design

3 He Fridge SPIRE WE Review Dec. 6-7, IFSI 16 External I/Fs, Budgets and connections WE Design I/F The Cryo cooler WE will be integrated in the analogue input/output DRCU board.It will share the board with other subsystems: the calibration targets (Photometer & spectrometer) and the thermometers subsystem. Interfaces of this board are DACs (output) and ADCs (input) towards the cold electronics set up, and digital (serial asynchronous low speed) with DRCU master controller (see DRCU & basic Interfaces presentations) BUDGETS The total peak budget for these functions is lower than 3.5 W : the direct sum of individual Processes, Recycling will never be done during calibration phase.

3 He Fridge SPIRE WE Review Dec. 6-7, IFSI 17 Model Definition EM: In the absence of cold operations for the EM. functions of the cooler will be handled by the focal plane simulator. AVM: Complete set of input and output boards associated to the AVM DRCU. S/W sequences for recycling and temperature regulation will be implemented. 2 complete models will be built. CQM:The addition of the QM cooler will constitute the CQM; providing the complete set of input/output functions. PFM: Part of the PFM DRCU (Thermometer board/analogue output board and S/W in the master controller) is the WE PFM. FS: Part of the FS DRCU (Thermometer board/analogue output board and S/W in the master controller) is the WE FS Development Plan

3 He Fridge SPIRE WE Review Dec. 6-7, IFSI 18 Model AIV Procedures One VG per Model. Description of the AIV steps: Diagram providing (for the model considered) indications on both the AIV steps and their respective inputs, the test means used and responsibilities. Development Plan

3 He Fridge SPIRE WE Review Dec. 6-7, IFSI 19 Test Equipements A subsystem interface simulator: this equipment will simulate the master controller dialog with the subsystem. It allows Master controller (H/W &S/W) and I/F board to be validated before integration with other subsytems. It also simulate the power load on the secondary power supply for Power Distribution Board and DC/DC converter tests purposes. A local test Unit: this equipment allows.command batches to be prepared and sent to the DRCU. It will feature thermometry visualisation. (see C;Cara presentation) Development Plan

3 He Fridge SPIRE WE Review Dec. 6-7, IFSI 20 Development Schedule (Model) One VG per Model. Gant Chart showing the main development task to be carried out for each model. Development Plan