# Presentation: 816230

## Phase II Major Tasks 

***Phase II Major Tasks ***

***Statement of Major Tasks***

***2. Interrogation Source & Power Supply***

- Design, fabricate, and assemble a gamma source
- Commission gamma source/power supply and perform acceptance test
- Produce specifications for procuring high current pulsed power supply (100A, 500Hz,1% duty factor)

## Phase II Milestones and Deliverables

***Refer to original project plan documentation***

***Phase II Milestones and Deliverables***

***Schedule with Milestones and Deliverables***

## Co-Axial Gamma/Neutron Source Concept

**D****+****/H****+**** Ion source chamber, made of Aluminum**

**cylindrical plasma chamber 30 cm ID, 15 cm tall    (drawing is not to scale)****‏**

**water-cooled ****Ti or B target**** at -180 kV**

**5 kV extraction electrode.  Not present when running high current for producing gammas (with slower rise and fall time). **

**RF antenna (quartz tubing with conductor inside)****up to 50 kW @ 2 MHz****20********s, 500 Hz, 1% duty factor**

- B

- e

- e

**Axial magnetic field to suppress 2****nd**** electrons**

***Gamma Source******  p-B target      180kV, 1A (avg)************ 10******8****** – 10******10****** ************ /s***
***Neutron Source****** D-D on Ti target 180kV, 0.1A (avg)************ 10******11******-10******12****** n /s***

***Phase II Technical Achievements***

## Torodial-Shaped Plasma Chamber

**Torodial-Shaped Plasma Chamber**

- Aluminum plasma chamber

- Water coolinglines

- Multicusp permanentmagnets to confine plasma

- RF antenna (quartz tube with conductor inside)

- Assist ignition with a hot filament

## Extracting Mutiple Beamlets Towards Center

**Extracting Mutiple Beamlets Towards Center**

- Plasma electrode & extraction grid(46% transparent, 92 slots5 mm x 60 mm, J ~ 225 mA/cm2)

*2 MHz RF frequency*
*50 kW RF power*
*2 - 5 mTorr pressure*
*225 mA/cm**2** **** 50A*
*20 ****s, 500 Hz*

## Low Power Target

**for 1⁄2 Hz Operation**
**500 Hz operation will require****a new high power target with****following design requirements:**
- Peak Power = 9.5 MW
- Average Power = 95 kW
- Average Power Density  250 W/cm2
- (50 A, 180 keV Protons)

**Low Power Target**

**LaB****6**** Tiles**
**(soldered or brazed****to target housing)**

**High Voltage Target Housing****(Provides Water Cooling)**

**12 SmCo Permanent Magnets**
**Provide Solenoidal Electron****Suppression Field****(~1 kG on Target Surface)**

**Electron Trajectories**
**(Top View)**

**Cooling Water Inlet and Outlet**
**(On High Voltage Potential)**

**Ceramic Vacuum-Tight**
**180 kV High Voltage Feedthrough**

## With Low-Power Target at Center

**With Low-Power Target at Center**

**Exchangeable Coaxial Target Geometry for****Maximum Beam Density and Smallest Footprint:**
- (LaB6 Tiles for Gammas, Ti for Neutrons)

## Assembled View

**Assembled View**

**Plasma Chamber with**
**Multicusp Magnets**

**Extraction Grid**

**Target**

**To Turbo Pump**

**Chamber Water**
**Cooling Lines**

**RF Antenna**

**Target Feedthrough**

## Layout

**-180 kV**
**Target Feedthrough**
**(incl. water connections)**

**HV Feedthrough to**
**Capacitor Bank Connection**

**Diala Oil Tank**

**Aluminum Plasma Vacuum Vessel, ******** ******** 61 cm **
**(incl. multicusp confinement magnets)**

**Plasma (H****+****)**

**Ion Beam**
**(****50 A peak****)**

**Water Cooled**
**Target Housing**

**Antenna**

**Plasma Electrode**
**(at ******** ******** 31 cm, 46% transparent)**

**LaB****6**** Target Tiles**
**(water cooled**
**at -180 kV,**
****** ******** ****18.4 cm****)**

**Electron**
**Suppression**
**Magnets**

**Support**
**Frame**

**Turbo**
**Pump**

**quartz tube with**
**conductor inside**
**2 MHz RF up to 50 kW**
**20 ********sec****, 500 Hz**
**1% duty factor**

**Layout**

## Slide 10

## Gamma Source High Voltage System

_**Gamma Source High Voltage System**_

**-180 kV****Power Supply**

**267 nF Capacitor Tank****at 20us, 100A,****voltage droops 4.2%.**

**Neutron/Gamma Source**

***Detailed Progress Status by Task***

## A -180kV high voltage power system for biasing the target and provides the beam accelerating potential.

***Detailed Progress Status by Task***

## 180 kV Capacitor Tank Hardware

**With 267 nF, a 20us, 100A****beam pulse will cause **
**the high voltage to droop 4.2%.**

***Detailed Progress Status by Task***

## RF Systems for the Ion Source

- Matching network to impedance match the RF power supply to the antenna is a unit built at LBNL with enough flexibility to match to various antenna configurations

- RF power supply to drive the antenna for the plasma ion source is a 2MHz, 50kW commercially available power supply

***Detailed Progress Status by Task***

## An extraction pulser was built and tested

- pulser chassis

- charging power supply

- resistive load

_**An extraction pulser was built and tested**_

- IGBTswitch array

- _pulser  chassis_

- 5 kV flat top (1kV/div).
- 5 A Current (2A/div.)

***Detailed Progress Status by Task***

- 500 Hz, 20 us (4 us/div.)

## To use prompt neutron signatures, the beam pulse must have a relatively fast fall time.  

- The fall time is determined by the load capacitance discharging through the load resistance (RC time constant).
- There is a trade off between decreasing the fall time and increasing the power needed to supply the extra current to a lower value load resistor.
- In the tested example, decreasing the fall time by a factor of 10 (2us to 0.2us time constant) increased the average power by the same factor (250W to 2.5kW)...the pulser has been tested for both conditions.

***Detailed Progress Status by Task***

## Full Power 180kV Power Supply from NWL

- Proposal 1 (preliminary)
- 2 power supplies in parallel and a separate capacitor tank
- Footprint = (10.4’x8’) + (4.1’x2.4’)
- Height = 7.1’
- Weight = (2x5k)+3k = 13k lbs.
- Oil = (2x200)+200 = 600 gal.
- Cost = 150k + 34k = 184k$
- *will use the LBNL capacitor tank which was not optimized for size and cost does not include LBNL engineering cost

- Proposal 2 (formal quote)
- 1 power supply with integrated capacitor bank
- Footprint = 7.7’x6.7’
- Height = 7’
- Weight = 12k lbs.
- Oil = 500 gal.
- Cost = 230.5k$
- *does not include door panel clearance

**High power tests require a 180kW power supply ****for 20us, 100A beam pulses at 500Hz **

***Detailed Progress Status by Task***

## Footprint of the second power supply proposal from NWL which integrates the capacitor bank.

***Detailed Progress Status by Task***

## Successful Initial Operational Testing

**The plasma was ignited with 45 kW RF power, at < 8 mTorr gas pressure, for up to 200 ********s, 10 Hz.**
**Summarize the results on applying high voltage**
**Summarize the results on beam extraction, if available**** **

- Replace with one showing the HV feed through.  Picture will be available on Monday

## LaB6 Tile

**LaB****6**** Tile**
**Heats up to 900 ********C**

**High Power Target**
**Requires Efficient****Water Cooling:**

**LaB****6**** Brazing Test:**

- OFHC Copper

- Mo Shim
- with PalCuSil15 BFM

- LaB6
- (Ni electropl.)

**Water Cooled Side**

- Peak Beam Power = 9.5 MW
- Average Power = 95 kW
- Average Power Density  250 W/cm2
- (50 A, 180 keV Protons)

## Remaining Issues

- Phase 2 was only 10 months long.  We have completed design and fabrication of the gamma generator.  More experimental work is needed.
- Measure gamma yield as a function of beam power.
- Increasing to 500 Hz (1% duty) will require a new target with a high voltage feed-through capable of high flow rate. The peak power density during the 20 s pulse is near 20kW/cm2.
- The procurement of a high average power 200 kV power supply has a 6-8 month delivery time.

## Future Work

- Optimize the ion source operation to achieve high current density with minimum gas pressure.
- Characterize beam extraction and optimize gamma yield by utilizing the narrow angular distribution.
- Test beam gating using the existing 5 kV pulser.
- Design and fabricate a high power target to allow 500 Hz operation.
- Reliability and durability test at 500 Hz (when the power supply becomes available).

## Gantt Chart