Building a CLP/CLA system is a multi-phase project.

Goal: Validate field topology calculations and CH_0 sensing with off-the-shelf components. Budget: ~£150–300. Time: 1–2 weekends.

1.1 Coil Assembly

Helmholtz pair (simplest multi-loop topology):

• Two identical circular coils, radius (a = 10) cm, separation (d = a) (optimal uniformity)
• Wire: 18–22 AWG enamelled copper (magnet wire), ~50–100 turns per coil
• Former: PVC pipe or 3D-printed ring
• Current: 1–3 A from a benchtop DC power supply (12–24 V, 5 A capable)

Winding:

1. Wind 50–100 turns tightly and evenly around the former
2. Secure with electrical tape or epoxy
3. Solder leads to banana plugs or screw terminals

Field estimate: For (N = 100) turns, (I = 2) A, (a = 0.1) m, on-axis center field is:

[ B = \frac{\mu_0 N I}{2a} \approx \frac{(4\pi \times 10^{-7})(100)(2)}{2(0.1)} \approx 1.26 \text{ mT} ]

This is in the measurable range for hobbyist Hall sensors. build-electronic-circuits

1.2 Power Supply

• Benchtop DC supply: 0–30 V, 0–5 A adjustable (e.g., Rigol DP832, ~£200 used; or cheaper 12 V/5 A LED driver, ~£20)
• Current limiting: Set to 2–3 A max to avoid overheating
• Polarity: Ensure both coils carry current in the same direction (azimuthally) for constructive superposition

1.3 CH_0 Sensor Array

Hall effect sensors for field mapping: build-electronic-circuits

• Linear analog sensors: SS49E, UGN3503, or A1302 (~£2–5 each)
  • Output: 0–5 V proportional to field strength
  • Sensitivity: ~1–5 mV/G (~10–50 mV/mT)
• Digital sensors: A3144 (on/off detection, ~£1)
• Microcontroller: Arduino Uno or Nano (~£10–15)

Wiring (SS49E example): luisllamas

SS49E Pinout:
Pin 1 (Vcc) → Arduino 5V
Pin 2 (GND) → Arduino GND
Pin 3 (OUT) → Arduino A0 (analog input)

Add 10kΩ pull-up resistor between Vcc and OUT if needed

Calibration code: luisllamas

const int hallPin = A0;
const float zeroFieldVoltage = 2500; // mV (check datasheet)
const float sensitivity = 1.3; // mV/Gauss (check datasheet)

void setup() {
  Serial.begin(9600);
}

void loop() {
  int reading = analogRead(hallPin);
  float voltage = reading * (5000.0 / 1023.0); // Convert to mV
  float gauss = (voltage - zeroFieldVoltage) / sensitivity;
  float mT = gauss * 0.1; // 1 Gauss = 0.1 mT
  Serial.print("B = ");
  Serial.print(mT);
  Serial.println(" mT");
  delay(500);
}

1.4 Field Mapping Procedure

1. Mount sensor on a 3-axis translation stage (or manual x-y-z rig)
2. Scan along the symmetry axis ((z)) and radial direction ((\rho))
3. Record (B(z)) and (B(\rho)) at 1–2 cm intervals
4. Compare measured values to your elliptic integral predictions (Section 3.1)

Expected outcome: Measured field should match theory within 10–20% (tolerances in winding, sensor calibration, and positioning account for discrepancies).

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Phase 2: Scaled Prototype (1–2 m Diameter, Enhanced Field)

Goal: Demonstrate a human-scale CLA with (B_{\text{safe}} < 1) mT and detectable CLP. Budget: ~£1,000–3,000. Time: 1–3 months.

2.1 Coil Geometry

Multi-loop hemispherical array (scaled-down version of your 12-loop design):

• Radius: (R = 1) m
• Loops: (N = 6) latitude rings at (\theta_i = 15°, 30°, 45°, 60°, 75°, 90°)
• Wire: 14–16 AWG magnet wire, 10–20 turns per loop
• Current: 5–10 A per loop (requires robust power distribution)

Support structure:

• PVC or aluminum hemispherical frame (cut pipes to latitude rings)
• 3D-printed or machined wire guides to maintain spacing
• Non-conductive fasteners (nylon bolts, zip ties)

2.2 Power Distribution

Parallel vs. series:

• Series: All loops carry same current, single high-current supply. Simpler, but voltage drop adds up.
• Parallel: Each loop has independent current control. More flexible, but requires current balancing.

Recommended: Series connection with a high-current DC supply:

• 12–24 V, 20–50 A capability (e.g., server power supply repurposed, ~£100–200)
• Bus bars or thick copper straps (6–10 mm²) to minimize resistive losses
• Fusing: 30–50 A fast-blow fuse per branch

Power dissipation estimate: For 14 AWG copper (~8 mΩ/m), 6 loops × ~6 m circumference = ~36 m total wire: [ R_{\text{total}} \approx 0.008 , \Omega/\text{m} \times 36 , \text{m} \approx 0.29 , \Omega ] [ P = I^2 R = (10 , \text{A})^2 \times 0.29 , \Omega \approx 29 , \text{W} ] Manageable with passive cooling, but coils will warm up after ~30 minutes of continuous operation.

2.3 Enhanced CH_0 Array

Multi-point sensing:

• 8–16 Hall sensors distributed throughout the interior and near the perimeter
• I2C or SPI multiplexing: Use an I2C GPIO expander (e.g., MCP23017) or analog multiplexer (e.g., CD4051) to read many sensors with one Arduino
• Data logging: SD card module or serial output to a laptop for real-time visualization

Optional upgrades:

• Fluxgate magnetometer (e.g., MAG-03, ~£300–500): Higher sensitivity (nT resolution), better for detecting small perturbations
• 3-axis sensors: MLX90393 or LIS3MDL (~£10–20): Measure (B_x, B_y, B_z) independently for full vector field reconstruction phys.ufl

2.4 CH_1/CH_2 Prototype

Warning and enforcement:

• CH_1 (warning): RF jamming module (e.g., 2.4 GHz jammer, check Ofcom legality first), high-power LED strobe, or piezo buzzer
• CH_2 (enforcement): For a non-superconducting prototype, you can’t achieve 10 mT disruption fields at 1 m scale without massive currents. Instead, demonstrate detection and alert:
  • When CH_0 detects a ferromagnetic object crossing the CLP (field perturbation > threshold), trigger CH_1/CH_2
  • Log the event, send an alert, or activate a camera

Legal note: In the UK, deliberate RF jamming is illegal without Ofcom authorization. Use acoustic or optical deterrents for lawful testing.

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Phase 3: Full-Scale Dome (10 m, Superconducting)

Goal: Realize the full CLP/CLA system as described in your document. Budget: £50,000–200,000+. Time: 6–18 months. Requires specialist collaborators.

3.1 Superconducting Coil Fabrication

NbTi wire sourcing:

• Suppliers: Bruker EAS, Oxford Superconducting Technology, or Furukawa (Japan)
• 规格: 1–2 mm diameter multifilamentary NbTi in copper matrix
• Cost: ~£50–100 per meter (estimate; request quotes)
• Total length: 12 loops × ~60 m each = ~720 m → £36,000–72,000

Winding:

• Mandrel: Aluminum or stainless steel former, precision-machined to latitude ring profiles
• Turn count: 10–20 turns per loop (your document assumes single-turn; multi-turn increases inductance and field)
• Insulation: Polyimide (Kapton) tape or epoxy impregnation
• Jointing: Superconducting solder (indium-based) or mechanical clamps with indium foil

3.2 Cryogenic System

Option A: Liquid helium bath (4.2 K)

• Cryostat: Custom vacuum vessel with liquid helium dewar
• Thermal shields: 77 K (liquid nitrogen) radiation shield
• Cost: £20,000–50,000 for a 10 m system
• Operating cost: Helium is expensive (~£10–20/L); boil-off losses add up

Option B: High-temperature superconductor (HTS) at 77 K

• Material: YBCO coated conductor or BSCCO tape
• Coolant: Liquid nitrogen (cheap, ~£1–2/L)
• Suppliers: American Superconductor, SuperPower Inc.
• Cost: HTS wire is pricier per meter (~£200–500/m) but cryogenics are simpler

Cryostat design:

1. Vacuum vessel: Stainless steel or aluminum, double-walled with vacuum insulation
2. Thermal anchors: Copper straps connecting coil to coolant reservoir
3. Quench protection: External dump resistors, voltage taps for quench detection
4. Instrumentation: Temperature sensors (Cernox, silicon diode), level sensors for cryogen

3.3 Persistent Current Switch

To operate in persistent mode (no external power supply):

1. Charge the coil: Connect to a high-current DC supply (100–500 A) via a superconducting switch
2. Close the loop: The switch is a short section of superconductor that can be heated above (T_c) (normal state) or cooled below (T_c) (superconducting state)
3. Persistent mode: Once the switch is superconducting, the current circulates indefinitely with (R = 0)

Switch design:

• Small heater (1–5 W) wrapped around a section of the coil
• Control circuit to apply heat during charging, then remove heat for persistent operation

3.4 Structural and Safety Engineering

Hoop stress:

For a 10 m loop at 5 kA, the magnetic pressure is: [ P_{\text{mag}} = \frac{B^2}{2\mu_0} \approx \frac{(0.1 , \text{T})^2}{2(4\pi \times 10^{-7})} \approx 4 , \text{kPa} ] This is modest, but mechanical reinforcement (aluminum or composite overwrap) is still recommended.

Quench management:

• Energy extraction: 8 kJ per loop must be safely dissipated if a quench occurs
• Detection: Voltage taps across each loop; if (V > 100) mV, trigger quench protection
• Dump resistor: External resistor (1–10 Ω) switched in parallel to absorb energy

Safety systems:

• Oxygen deficiency monitoring: Cryogen boil-off can displace air in enclosed spaces
• Magnetic field signage: Warn of strong fields (pacemakers, magnetic media)
• Access control: Interlocks to prevent entry when field is active

3.5 CH_0/CH_1/CH_2 Integration

CH_0 (observer):

• SQUID magnetometers (if budget allows): nT sensitivity, but require their own cryogenics
• Fluxgate arrays: Practical alternative, ~£500–1,000 per sensor
• Data acquisition: National Instruments DAQ or custom FPGA-based system for real-time monitoring

CH_1 (warning):

• RF detection: SDR (software-defined radio) to detect drone telemetry (2.4 GHz, 5.8 GHz)
• Acoustic deterrent: High-power sirens or ultrasonic emitters
• Optical: Strobe lights or laser illumination (Class 3B, eye-safe)

CH_2 (enforcement):

• Variable-field mode: If not using persistent current, ramp up current in outer loops to increase (B_{\text{crit}}) at the perimeter
• Legal compliance: Ensure any active disruption (RF jamming, high-field pulses) is authorized under UK law

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Phase 4: Iterative Refinement

Once the system is operational:

1. Map the field: Use a 3-axis magnetometer on a drone or robotic arm to measure (B(\rho, z)) throughout the volume
2. Tune thresholds: Adjust (B_{\text{safe}}) and (B_{\text{crit}}) based on measured field and drone disruption tests
3. Optimize loop currents: Use your eigenmode analysis (Section 8.4) to sculpt the CLP shape
4. Automate governance: Implement the CH_0 → CH_1 → CH_2 state machine in firmware (e.g., STM32 or Raspberry Pi Pico)

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Quick-Start Checklist (Phase 1)

First milestone: Power the Helmholtz pair to 2 A, measure ~1 mT at the center with the Hall sensor, and confirm the field drops off as predicted by the Biot-Savart law .