introduction to the gatling gun development program

Gatling gun program review, June 28th-29th, 2012

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Introduction to the Gatling Gun Development Program

Report to the Gatling Gun Review CommitteeBy

John SkaritkaJune, 28, 2012

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Talk outline

• Program Motivation

• Gatling Gun Concept Schematic and System Layouts

• Gun Parameters list

• Goals and challenges of the Phase 1 R&D

• Scope of the short term R&D program 2010-2012

• Layout of G-Gun Lab in 905

• Schedule 2012 -2013 feasibility studies

• Summary and Acknowledgments



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Motivation• 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 mA 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.


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Motivation continued

• 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.

• This LDRD program is one of the “highest priority” items as set by EICAC.

• It is complementary to high-current sources R&D at Jlab and MIT, if successful it can serve as a multiplier to developments by others.

• It is a unique, new approach toward enhancing current capability in polarized electron sources.

• If successful the Gatling Gun may be used as a polarized electron source for the proposed e-RHIC machine.


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30 deg

Combiner, 704 kHz rotating dipole and quadrupole fields

Bunching cavity (112 MHz)

3rd harmonic cavity Ballistic

compressionBooster linac

Gatling gun

“Gatling Gun” concept

2 to 20 Photo-cathodes arranged in a ring

16 cm

Fixed bend magnets

G-Gun Laser System (two shown)

Target photo current to be 2.5 mA / cathode, beam current to be > 50 mA @ 200 kV

200 kV electron beam


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How the Gatling Gun may appear in e-RHIC

Bunching cavity (112 MHz)

Pair of Gatling guns Ballistic compression

Depicted in the 2 o’clock hall of the RHIC tunnel

RHIC Ion beam line e- RHIC superconducting RF cavities


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Gatling Gun System Layout

Cathode Exchange Chamber

Extreme vacuum chamber

Gun Laser System table, (Laser Lab not Shown)

Cathode Transport Line

Cathode Prep.Chamber( Grand Central )

Cathode Regeneration Forest

Fresh Cathode Load Lock

250 KV Feed through


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Layout of Phase 1 Gatling Gun Developmental SystemHigh Voltage

Feed through

TransitionSection

Depressed Collector

Combiner Magnet

Beam Diagnostic

sectionMain gunchamber

Cathode array

injector

Cathode Exchange Chamber

Cathode preparation system (Grand Central)

22 cathode train

Manipulator to move cathodes between train and prep trees

Atomic hydrogen gun

Cathode service flange assembly to heat, cool and apply O2

System to deposit Cs on the cathode

cathode module

Cathodes Preparation Trees Assy.



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Sectioned View of the Gatling Gun shows the cathode train from the Cathode Prep. Chamber (upper left) arriving 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.).

Cathode Prep. Chamber20 Cathode Shroud(Revolver)Injectable Cathode MagazineCathode Module Manipulator

Cathode TrainCathode Exchange Chamber(CEC)

path of motion


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Cathode, Anode G-Gun Component design

1st Bend Dipole Stainless steel Cathode Shroud < 250KV

Titanium Anode Focusing Solenoid

Gallium Arsenide Cathode

Molybdenum cathode base

Titanium conformer

Extreme Vacuum Cathode Ring NEG pump

Cathode Module Cathode cooling ring

4W, 780 nm Laser Beam

2.5 mA. Electron Beam


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Two Beam Combiner operation and diagnostics

The Combiner design will be presented by Erdong Wang and Diagnostics will be presented by David Gassner later today.


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R&D Gatling Gun Parameters List Page 1Electron Beam Parameters

Reference design beam energy -220 keVCharge per bunch 3.5 nCBunch length (FWHM) 1.5 nsThermal emittance per mm of incident beam 0.22 mm-mradminimum no. of cathodes for LDRD completion 2

High Voltage systemMaximum operating Voltage -250 kVNominal voltage grad. At cathode 6MV/mmaximum voltage grad. Cathode shroud and Anode 12MV/mmax. voltage grad. Invac. HV surface and XHV chamber wall <7MV/mmax energy in any discharge limited to < 10 joules

LaserLaser spot size on cathode 8mmLaser pulse length, adjustment (FWHM) 1.5 nsLaser wave length 780 nmLaser power on cathode surface @704 kHz 2 wattsEnergy per pulse 2.7 µjoules

Laser WindowMin Aperture through Anode tube 15 mmMax. Aperture at laser entry window 20 mmwindow material 0 degree sapphiremin. incidence angle on vacuum side of window 1 degree

CathodeMaximum beam diameter on cathode 8 mmMaximum Ga As cathode size (square) 10 mmNominal Current per cathode 2.5 mANominal quantum efficiency >1%single cathode repetition rate 704kHzmaximum field on cathode < 1.5 gaussnominal distance between cathode and full solenoid field 35 mmVolts across 100µm gap on cathode surface < 1000 Vnom. Peak power deposited in cathode. 2000 wattsAvg.ohmic losses into cathode surface 0.3 wattsmin. cooling per cathode(steady state) 100 wattsCathode shroud cooling DI water max absorption of laser power into cathode surface 0.3 wattsmaximum ave.power deposited into cathode surface < 1 wattmaximum expected Temp rise on Cathode surface < 10 C


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R&D Gatling Gun Parameter List Page 2

Solenoid

solenoid, integrated field 0.26 T-cm

max field strength in solenoid 660 gausssolenoid aperture 20 mm

iron length 50mm

Clear aperture through solenoid 16 mm

Vacuum Parameters

Gun chamber wall and flange primary material 316L SST

Stainless chamber material vacuum prebake (12Hrs) 950 C

maximum out gassing rate of Gun Chamber XHV surfaces <2 X10^-13 Tl/s-cm^2

Main Gun Chamber approx. XHV surface area 24000 cm^2

Main Gun Cathode chamber Ion pump capacity 2000 l/s

NEG pumping speed in main Gun chamber >8000 l/s

Target vacuum in Main Gun chamber 6x10^-13 Torr

NEG pumping speed at cathode array 2000 l/s

Target Vacuum level at Cathode surface < 5x10^-13 Torr

Exchange Chamber approx. XHV surface area 20000 cm^2

NEG pumping speed in exchange chamber 4000 l/s

Exchange Chamber approx. XHV surface area 20000 cm^2

Target vacuum in exchange chamber 1x10^-12 Torr

Transition Chamber approx. XHV surface area 13000 cm^2

Target vacuum in transition chamber < 1x10^-11 Torr

Gun and exchange chamber assy. max bake temperature 400 C

transition chamber ion pump capacity 100 l/s

Solenoid

solenoid, integrated field 0.26 T-cm

max field strength in solenoid 661 gausssolenoid aperture 21 mm

iron length 50mm

Clear aperture through solenoid 17 mm

1st bend nom. magnetic length 95 mm

Peak field strength in 1st bend dipole 110 gauss

integrated field strength 0.93 T-mm

nom. ampere-turns 170 A-Tns.

good field region radius 5 mm

Static dipole coil resistance 0.4 Ω

Nom. Current 1 Amp.Bend 1 cooling Air


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R&D Gatling Gun Parameter List Page 3Combiner

Combiner rotating dipole field frequency 704 kHzCombiner vacuum chamber aperture 165 mmChamber material Aluminacombined clear bore aperture 186 mmferrite core OD 265 mmferrite core ID 215 mmferrite length 200 mmFerrite material (CMI) MN8CXNominal magnetic dipole field in Combiner 26 gaussGood field region radius 60 mmPeak current in combiner dipole coil 60 AmpsPeak current in combiner quadrupole coil 3 AmpsPower loss in coil 600 wattstime averaged power loss in ferrite core 650 wattswinding inductance < 10µHyamplifier power 300 wattsamplifier stored energy 0.018 joulescapacitor value 5.1 nFCooling DI water

Diagnostics ParametersTransverse Profile Screen (plunging) 45mm coated YAG:CeTransverse beam waist size at screen (round beam dia.) 15mmElectron Bunch Charge measurement ICT & ceramic breakHalo measurement Quad scraper upstream collectorGun & Dump current Curent transformer on HV câbles

Collector Parametersmax.neg. bias on floating supplies in collector circuit -20 kVnom. voltage at collector -200 kVnom. voltage at repeller -260 kV

Beam Transport Parametersnominal beam height 1.4mTransport length <4m


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Specific Goals of Phase 1 R&D

• Demonstrate multi-cathode Gun operation– Determine a practical minimum current per cathode

• Establish production of GaAs G-Gun Cathodes– Determine practical cathode Life – Determine potential cathode production through put.


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Technical challenges of the R&D program

• Demonstrate Prerequisite XHV properties in large Gun Chambers manufactured in industry

• Demonstrate operation of system components– Multi Cathode Drive laser system – Rotating field of a combiner magnet– A practical XHV valve


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Single Cathode Preparation system

The first piece of Gatling Gun equipment, the single cathode preparation system has arrived at BNL and is under bake out and testing in building 966.

Eric Riehn will be describing the system in his up coming talk and showing the system during a tour later today

single Gatling gun cathode module


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Phase 1 G-Gun module Layout

High Voltage LineGatling Gun

Gun Laser optics Vertical Bread Board

Depressed Collector

Combiner Supply

250 KV, supply


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Layout of Gatling Gun Lab. in building 905 Clean Room

Portable cranes

Multi-Cathode preparation system

Aluminum HV containment Room

Phase 1 Gatling Gun Module

Gatling Gun Laser Lab


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Schedule Milestones for 2012-13

• Grand Central Vessel vacuum Spec achieved……..……..……….3/2012• Single Cathode Prep system delivery and setup…………………6/2012• Gatling Gun vacuum system components completed …….....9/2012• 1560 nm laser operation at BNL………………………………………….9/2012• Grand Central manipulators integrated and XHV tested……10/2012• Cathode Shroud system and Anode Assembly completed…12/2012• Gatling Gun vacuum system integrated and XHV tested……..2/2013• 780 nm doubling operation ……………………………………………….2/2013• HV testing of completed Gatling Gun……………………….…….… 3/2013• Gun Cathodes routinely produced in single prep system......4/2013• Laser Lab and gun room assembled in building 905 …………..5/2013 • Phase 1 Combiner magnet completed……………………………...6/ 2013• Depressed collector assembled and tested………………………..7/2013• Diagnostics assembled and tested……………………………………..9/2013• Combiner power supply assembled and tested ………………..10/2013• High voltage supply system assembled and tested…………….11/2013• Gun beam line assembled in 905……………………………..………..12/2013


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Longer term Milestones, 2014-15 Prototype Development

• Gun vacuum system pump down and bake out…………………………….........1/2014• Gun system at XHV and system testing commences………..…………………..2/2014• One and two Cathode operation start………….……………………………….......3/2014• Grand Central (GC) Trees produced and integrated……..……………….……..4/2014• Multi -laser and Cathode Gun operation start.………………....................…6/2014• Cathode Prep chamber with Multi-cathode operation………………….......7/2014• GC Multi-Cathode production start…………………………………..………………...8/2014• Transport line system between GC and Gun chambers.………...............10/2014• Gatling Gun, transport and GC systems fully XHV integrated…………….11/2014• Phase 2 Combiner 700KHz tested and installed………….……. ……………... 2/2015• Gatling Gun full system operating under full test conditions………..……...4/2015• Full system performance , cathode life and throughput measured……...9/2015


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Summary

• Presented is an introduction of the Gatling Gun Development Program.• The R&D Goals and Challenges have been presented.• The design and operation of the Prototype Gatling Gun and

Cathode Prep system was presented. • The single Cathode preparation system completed and under test

at BNL.• Progress is being made on the Gatling Gun vessel components in

industry.• Schedule milestones that define the program have been presented

that if adequately supported will fully demonstrate and categorize the Gatling Gun system for use as a practical source for an ERL by the Fall of 2015.


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Acknowledgments

I. Ben-Zvi, J.C. Brutus, D. Gassner, B. Lambiase, V. Litvinenko, P. Manning

D. Pate, A. Pikin, T. Rao, O. Rahman, E. Riehn, T. Seda B. Sheehy, E. Wang, Q. Wu,

As well as the management and staff at the following firms,

MDC Corporation, Transfer Engineering Inc., Atlas Technologies, SAES Getters, Thermionics,

Pascal Technologies, Gamma Vacuum, Stangenes Industries

introduction to the gatling gun development program

Documents

gun lab

kvgatling gun program

highcurrent polarized

ldrd program

ma cathode

current capability

highcurrent sources

short term rd program