The Gatling Gun A High Current Polarized Electron

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“The Gatling Gun” A High Current Polarized Electron Gun System John Skaritka Collider-Accelerator Department

“The Gatling Gun” A High Current Polarized Electron Gun System John Skaritka Collider-Accelerator Department Brookhaven National Laboratory 1

Outline • Overview • Next generation scientists of the project • Description of Gatling

Outline • Overview • Next generation scientists of the project • Description of Gatling Gun system components and their operation • Summary 2

Overview • • • This is a Laboratory Directed Research and Development (LDRD) project.

Overview • • • This is a Laboratory Directed Research and Development (LDRD) project. The motivation is to develop a high-current polarized electron gun aimed at e. RHIC, where the requirement is 50 m. A average current. The specific approach is to use funneling of beams from multiple cathodes in order to increase the (current * lifetime) product of the gun. The goal of the LDRD project is to demonstrate that funneling works. To be specific: • A reasonable current and lifetime achieved with one cathode. • The addition of a second cathode does not degrade the performance of the first and thus doubles the current*lifetime product of the device. A separate LDRD project is devoted to the development of the laser driver. This program is complementary to high-current polarized gun R&D at Jefferson Laboratory and at MIT, i. e. advances in each of the programs lead to a combined improvement in the e. RHIC polarized injector. 3

Training next generation scientists Eric Riehn, Post Doc Develop and measure performance of optimized

Training next generation scientists Eric Riehn, Post Doc Develop and measure performance of optimized photocathodes and manufacturing processes for the Gatling Gun. Erdong Wang, Post Doc Electro magnetic and beam dynamic codes and photocathode preparation and testing Omer Rahman, Ph. D Student VORPAL code modeling to study 3 -D beam dynamics and cathode development and testing 4

“Gatling Gun” concept 20 Photo-cathodes arranged in a ring Gatling gun Fixed magnetic bending

“Gatling Gun” concept 20 Photo-cathodes arranged in a ring Gatling gun Fixed magnetic bending Target photo current to be 2. 5 m. A / cathode, beam current to be > 50 m. A @ 200 k. V Bunching cavity (112 MHz) 3 rd harmonic cavity Ballistic compression Booster linac 30 deg 16 cm Combiner, 700 k. Hz rotating magnetic bending G-Gun Laser Systems 5

Gatling Fun Feasibility system with diagnostic section and Depressed Collector Gatling gun chamber Combiner

Gatling Fun Feasibility system with diagnostic section and Depressed Collector Gatling gun chamber Combiner Diagnostic insertion Depressed Collector 6 6

Functions of the Preparation Chamber Manipulator to move cathodes between train and prep trees

Functions of the Preparation Chamber Manipulator to move cathodes between train and prep trees Cathodes Preparation Trees Assy. Atomic hydrogen gun System to deposit Cs on the cathode Cathode service flange assembly to heat, cool and apply O 2 24 cathode train cathode module 8

Sectioned View of the Gatling Gun Assembly shows, From left, the cathode train from

Sectioned View of the Gatling Gun Assembly shows, From left, the cathode train from the Cathode Prep. Chamber arrives in the Cathode Exchange Chamber lower right. A manipulator transfers the individual cathode modules from the train to the cathode magazine to be is injected into the 20 Cathode Shroud (revolver assy. ). “Grand Central” Cathode Prep. Chamber 20 Cathode Shroud(Revolver) Inject able Cathode Magazine Cathode Module Manipulator Cathode Train Cathode Exchange Chamber(CEC) path of motion 9

Cathode, Anode G-Gun Component design Titanium Anode Focusing Solenoid “C” Style 1 st Bend

Cathode, Anode G-Gun Component design Titanium Anode Focusing Solenoid “C” Style 1 st Bend Dipole Copper Cathode Shroud < 250 KV Cathode cooling ring Cathode Module 4 W, 780 nm Laser Beam Titanium conformer Molybdenum cathode base 2. 5 m. A. Electron Beam Gallium Arsenide Cathode Extreme Vacuum Cathode Ring NEG pump 10

E-beam transport through the combiner DC Dipoles bend the e-beams into a synchronized field

E-beam transport through the combiner DC Dipoles bend the e-beams into a synchronized field rotating at 704 KHz that bends the beam trajectory onto a common axis. 11

The drive laser Laser undergoing final testing at Optilab LLC of Phoenix AZ, and

The drive laser Laser undergoing final testing at Optilab LLC of Phoenix AZ, and Covesion Ltd, . of Hampshire, UK. Delivery expected shortly Pulsar with Phaselocked loop Accelerator RF ref Multi-stage EDFA Periodically – poled Li. Nb. O 3 4 W 780 nm Electrooptic modulator CW DFB laser 10 W 1560 nm Frequency doubling module A 1560 nm laser (CW DFB) is modulated synchronously with a subharmonic of the accelerating RF. After amplification in an Erbium-doped fiber amplifier chain (EDFA), the light is frequency doubled in periodically poled Lithium Niobate. The output will be 4 Watts at 704 k. Hz (5. 4 u. J/pulse), with an adjustable pulse width of 1. 2 -1. 7 nsec. 12

Summary A brief overview of the conceptual design and operation of the Prototype Gatling

Summary A brief overview of the conceptual design and operation of the Prototype Gatling Gun and Cathode Prep system was presented. Progress is being made on the Gatling Gun components in industry • • l l • XHV manufacturing practices have been developed and implemented in Industry. Detailed designs of Gatling Gun components are underway, some components are being manufactured while others are being tested. Schedule milestones that define the program have been presented that if funded will fully demonstrate and categorize the Gatling Gun for use as a practical source for an ERL by the Fall of 2015 13