Introduction to the Gatling Gun Development Program

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Introduction to the Gatling Gun
Development Program




Report to the Gatling Gun Review Committee

By

John Skaritka

June, 28, 2012

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

1


Talk outline





Program Motivation




Gatling Gun
C
oncept
S
chematic and
S
ystem Layouts




Gun
P
arameters 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

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

2

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.


Gatling gun program review, June 28th
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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.


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

4

30 deg

Combiner,
704
kHz
rotating dipole
and quadrupole fields

Bunching cavity
(112 MHz)

3
rd

harmonic
cavity

Ballistic
compression

Booster
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

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

5

200 kV electron beam

How the Gatling Gun may appear
in
e
-
RHIC


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

6

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

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

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

7

L
ayout
of
Phase 1
Gatling
Gun
Developmental System



High Voltage


Feed through

Transition

Section

Depressed

Collector

Combiner

Magnet

Beam


Diagnostic


section

Main gun

chamber

Cathode


array


injector

Cathode


Exchange

Chamber

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

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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
.

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

9

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
inj
ected into
the 20 Cathode Shroud (revolver assy.).

Cathode Prep. Chamber

20 Cathode Shroud(Revolver)

Injectable Cathode Magazine

Cathode Module Manipulator

Cathode Train

Cathode Exchange Chamber(CEC)



path of motion

Gatling gun program review, June 28th
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10

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

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12

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

R&D Gatling Gun
Parameters
List
Page
1


Electron Beam Parameters

Reference design beam energy

-
220 keV

Charge per bunch

3.5 nC

Bunch length (FWHM)

1.5 ns

Thermal emittance per mm of incident beam

0.22 mm
-
mrad

minimum no. of cathodes for LDRD completion

2

High Voltage system

Maximum operating Voltage

-
250 kV

Nominal voltage grad. At cathode

6MV/m

maximum voltage grad. Cathode shroud and Anode

12MV/m

max. voltage grad. Invac. HV surface and XHV chamber wall

<7MV/m

max energy in any discharge limited to

< 10 joules

Laser

Laser spot size on cathode

8mm

Laser pulse length, adjustment (FWHM)

1.5 ns

Laser wave length

780 nm

Laser power on cathode surface @704 kHz

2 watts

Energy per pulse

2.7 µjoules

Laser Window

Min Aperture through Anode tube

15 mm

Max. Aperture at laser entry window

20 mm

window material

0 degree sapphire

min. incidence angle on vacuum side of window

1 degree

Cathode

Maximum beam diameter on cathode

8 mm

Maximum Ga As cathode size (square)

10 mm

Nominal Current per cathode

2.5 mA

Nominal quantum efficiency

>1%

single cathode repetition rate

704kHz

maximum field on cathode

< 1.5 gauss

nominal distance between cathode and full solenoid field

35 mm

Volts across 100µm gap on cathode surface

< 1000 V

nom. Peak power deposited in cathode.

2000 watts

Avg.ohmic losses into cathode surface

0.3 watts

min. cooling per cathode(steady state)

100 watts

Cathode shroud cooling

DI water

max
absorption
of laser power into cathode surface

0.3 watts

maximum ave.power deposited into cathode surface

< 1 watt

maximum expected
Temp rise on Cathode surface

<
10


C

Gatling gun program review, June 28th
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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 gauss

solenoid 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 gauss

solenoid 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

Gatling gun program review, June 28th
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R&D Gatling Gun Parameter List Page 3


Combiner

Combiner rotating dipole field frequency

704 kHz

Combiner vacuum chamber aperture

165 mm

Chamber material

Alumina

combined clear bore aperture

186 mm

ferrite core OD

265 mm

ferrite core ID

215 mm

ferrite length

200 mm

Ferrite material (CMI)

MN8CX

Nominal magnetic dipole field in Combiner

26 gauss

Good field region radius

60 mm

Peak current in combiner dipole coil

60 Amps

Peak current in combiner quadrupole coil

3 Amps

Power loss in coil

600 watts

time averaged power loss in ferrite core

650 watts

winding inductance

< 10µHy

amplifier power

300 watts

amplifier stored energy

0.018 joules

capacitor
value

5.1 nF

Cooling

DI water

Diagnostics Parameters

Transverse Profile Screen (plunging)

45mm coated YAG:Ce

Transverse beam waist size at screen (round beam dia.)

15mm

Electron Bunch Charge measurement

ICT & ceramic break

Halo measurement

Quad scraper upstream collector

Gun & Dump current

Curent transformer
on HV
câbles

Collector Parameters

max.neg. bias on floating supplies in collector circuit

-
20 kV

nom. voltage at collector

-
200 kV

nom. voltage at repeller

-
260 kV

Beam Transport Parameters

nominal beam height

1.4m

Transport length

<4m

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

15

Specific Goals of Phase 1 R&D


Demonstrate multi
-
cathode Gun operation


Determine a practical minimum
c
urrent per cathode


Establish production of GaAs G
-
Gun Cathodes


Determine practical cathode Life


Determine potential cathode production through put.



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

16

T
echnical
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


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

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Single Cathode Preparation system

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

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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

s
ingle Gatling
g
un
cathode module

Phase 1 G
-
Gun module Layout

High Voltage Line

Gatling Gun

Gun Laser optics

V
ertical Bread Board

Depressed
Collector

Combiner Supply

250 KV, supply

Gatling gun program review, June 28th
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Layout
of Gatling Gun Lab.
i
n building 905
C
lean Room

Portable cranes

Multi
-
Cathode
preparation system

Aluminum HV
containment Room

Phase 1 Gatling Gun Module

Gatling Gun Laser Lab

Gatling gun program review, June 28th
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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


Gatling gun program review, June 28th
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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

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

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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.


Gatling gun program review, June 28th
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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




Gatling gun program review, June 28th
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