STATE-OF-THE-ART ELECTRON GUNS AND INJECTOR DESIGNS
FOR ENERGY RECOVERY LINACS (ERL)
Alan Todd
Advanced Energy Systems
P.O. Box 7455, Princeton, NJ 08543-7455, U.S.A.
Corresponding author: Alan Todd
Phone: 609-514-0316 ; FAX: 609-514-0318 ; e-mail: alan_todd@mail.aesys.net
ABSTRACT
A key technology issue of energy recovery linac (ERL) high-power free-electron laser
(FEL) and fourth generation light sources is the demonstration of reliable, high-brightness, highpower injector operation. Ongoing programs that target up to 0.5 Ampere injector performance
at emittance values consistent with the requirements of these applications, are described. There
are three approaches that could deliver the specified performance. These are DC photocathode
guns with superconducting RF (SRF) booster cryomodules, high-current normal-conducting RF
(NCRF) photoinjectors that may also use SRF boosters, and SRF photocathode guns and
boosters. The achieved performance at existing ERL facilities, the status of ongoing source
development programs, and the proposed parameters of the injectors for planned ERL facilities
are described and compared. As examples, we concentrate on three high-current injectors being
developed by Advanced Energy Systems (AES) with collaborators at the Thomas Jefferson
National Accelerator Facility (JLAB), Los Alamos (LANL) and Brookhaven (BNL) National
Laboratories.
PACS: 29.17.+w, 29.27.AC, 41.85.Ja, 85.60.Ha
Keywords: Photoinjector, Electron Gun, DC Gun, High-Average-Current, Superconducting
Radio Frequency (SRF), Energy Recovery Linac (ERL).
1.
INTRODUCTION
Although the ERL concept had been in existence for many years [1,2,3,4], the spark
that spawned many of the ERL devices discussed below was the success of the JLAB ERL
IR FEL [5]. Today, there are three active ERL facilities: the JLAB IR FEL Upgrade [6], the
ERL FEL at the Japan Atomic Energy Research Institute (JAERI) [7] and the Budker Insitute
for Nuclear Physics (BINP) Recuperator at Novosibirsk [8]. Near term ERL facilities under
construction include the NSF-funded Cornell [9] and UK Daresbury ERL-Prototype [10]
devices.
Table 1 lists the principle injector specifications for these and other relevant
devices, past, present and future, from which, in Table 2, we will later construct nominal
parameter requirements and associated ranges for ERL injectors. The three columns in
yellow are the injectors in development at AES that will be discussed in greater detail below.
The devices on the left of the table all use DC guns as indicated by “Gun Type”.
These include the active JLAB [6], JAERI [7] and BINP [8] FELs. For the JLAB column,
the parameters in parentheses are the values at the wiggler, while the first number in each
case is the inferred value after the injector. For BINP and JAERI, the achieved numbers are
shown first with projected near-term upgrade values in parentheses. The Cornell ERL [9]
injector targets 100 mA average current while the Daresbury ERLP [10] is very similar to the
current JLAB device. Both these devices are presently under construction. KEK [11] are
developing an ERL concept that is similar to that of Cornell and is not separately listed here.
JAERI and BINP use thermionic guns as opposed to the photocathode guns of the other
injectors, though JAERI are actively developing a photocathode gun to improve the
achievable beam brightness, a key to high-performance for all ERL FELs or light sources. In
each case, Gallium Arsenide is the photocathode material of choice for these DC guns. The
other listed DC gun and booster consists of a JLAB DC gun and an AES SRF booster that is
1
presently being assembled for testing at the JLAB injector test stand beginning in 2006, and
which is described in greater detail below.
The next three injectors utilize normal-conduction RF (NCRF) guns. It is interesting
to appreciate that at 32 mA, the Boeing gun [12,13] shown in Fig. 1 and now retired, which
operated at 25% duty factor with a macropulse current of 132 mA, is still the demonstrated
high-average-beam-current state-of-the-art despite the recent focus on DC guns. Below, we
describe the LANL/AES 700 MHz NCRF Glidcop® gun that is in fabrication for thermal
testing at LANL in early 2006. The nominal operating current for this gun is 100 mA with a
33.3 MHz laser pulse repetition rate (PRF).
However, as shown by the figures in
parentheses, the same gun, operating at 350 MHz PRF, could, in principle, deliver more than
1 A of average current with the identical thermal load and stress. The “LUX” project [14] at
Lawrence Berkley National Laboratory (LBNL) optimized the cell shaping to design an
NCRF gun that delivers improved impedance to lower the thermal loads and stress, thereby
permitting the use of OFE copper in place of Glidcop®, which can be difficult to braze.
The Boeing gun used a Cesium Potassium Antimonide multi-alkaline cathode
material. Multi-alkalis are the cathodes of choice for these guns because, as compared to DC
guns, the operating vacuum cannot be maintained high enough to permit the use of GaAs.
Additionally, for any ERL injector, it is almost mandatory that one use a cathode that
responds to green, as opposed to UV, illumination to make the photocathode drive laser
tractable, reliable and affordable. The specifics of cathode issues for ERL injectors are
addressed in the parallel Reference [15].
Finally, there is growing interest in SRF injectors following the pioneering work of
Forschungszentrum Rossendorf, (FZR) [16], albeit at lower current than desired for proposed
ERL devices.
However, AES is fabricating a 703.75 MHz half-cell SRF gun, in
collaboration with BNL, that is being designed to deliver 0.5 A. In addition to multi-alkalis,
2
the novel diamond cathode concept [17] is being considered for this gun. The figures in
parenthesis show the significant improvement in the longitudinal beam quality that results
from linearizing the longitudinal phase space with a harmonic RF cavity.
While this
technique can be usefully applied to all injector technologies, none of the other columns
includes such optimization. This is one of the three injectors described in more detail below.
The final column describes the plans for 4GLS proper as opposed to the ERLP. Here,
the desire is to use an SRF gun with a diamond cathode for high-average current operation
and most likely an NCRF gun for the alternate high-brightness operation shown in
parentheses [18].
The table also indicates what type of booster is planned for each injector unless it is
not applicable (N/A). The geometry of the booster in terms of cells per cavity, the power
coupling technique and the power level per feed used or planned, whether coaxial (CX) or
waveguide (WG), is also shown.
In addition to FELs and light sources, there are other ERL and high-current injector
applications that have not been specifically included in Table 1. The AES/BNL SRF gun
operates at a harmonic of the RHIC frequency and will be a key element of a 0.5 A highcurrent ERL test at BNL in 2007. There are two goals for this work [19]: firstly to develop a
gun for electron cooling of hadron storage rings such as the Relativistic Heavy Ion Collider
(RHIC); and secondly to provide high-intensity electron beams for high-luminosity colliders
such as e-RHIC and ELIC. Because of the existing RHIC parameters, electron cooling
requires 20 nC bunches at 9.4 MHz for an average current of ~200 mA. Hence the ideal
injector for this application is not the above 0.5 cell SRF gun, which will however
demonstrate the viability of the technology, but rather a 1.5 cell SRF gun without a booster
accelerator that accelerates the beam to 5 MeV. The e-RHIC collider calls for up to 16 nC
3
bunches at 28.15 MHz for an average current up to 450 mA, and would utilize a similar 1.5
cell gun for the injector.
2. INJECTOR OPTION COMPARISON
In looking towards the future, we have combined the Table 1 specification for all the
photocathode injectors that plan to operate near or above 100 mA. Table 2 shows the
resultant nominal “requirements” that are being requested for the principal ERL injector
parameters, together with an associated range. This table shows that the proposed highcurrent ERL facilities have much in common.
It is also clear that there are three injector technologies being seriously considered for
ERL facilities, namely: DC, NCRF and SRF guns that will likely be followed by SRF
boosters. We do not discuss injector variants and hybrids [20] that utilize coaxial coupling
[21,22] or doubly-resonant guns [23,24] that may some day find application in ERL devices.
Of the three candidate technologies, the DC gun is the most mature with 10 mA CW
already demonstrated at JLAB and 100 mA injectors in fabrication at Cornell and
AES/JLAB.
Recent Cornell simulations for optimized DC gun configurations show
exceptional performance with transverse emittance values significantly lower than 1 µm at
the nominal 77 pC charge level [25]. The achievable gradient and voltage with respect to
field emission and breakdown may be limited to around 7 MV/m and 500 kV though Cornell
plan to stretch these limits experimentally. There will also be a gradient limit set by dark
current in these guns. The very high-vacuum capability of the DC gun does lead to a viable
cathode option in GaAs, whose performance and lifetime today are limited by ion backbombardment. The 400 C drawn from such a cathode between recesiations [5] corresponds
to over an hour of operation at 100 mA, which is not sufficient for ERL facility operation at
4
high availability, but is still very promising. Consequently, it appears likely that DC guns
coupled with SRF boosters will be capable of delivering the required ERL injector
performance.
The maximum achievable gradient in CW NCRF guns is limited to around 10 MV/m
due to thermal stress limits. There is also an efficiency penalty and associated cost due to the
impedance and resistive losses.
Achievable vacuum conditions limit visible cathode
selection to multi-alkaline materials or diamond amplifiers and raise issues of achievable
performance and lifetime. However, we noted that the Boeing injector was still the state-ofthe-art for high-average current gun operation and it serves as a proof-of-concept for NCRF
injectors at current levels approaching 100 mA, and with higher beam-loading and PRF,
ampere-level operation at the same engineering stress level and beam dynamics performance.
The SRF gun, which can, in principle, deliver RF gun performance with DC gun
efficiency is the least mature but also the most desirable ERL injector option. The maximum
achievable accelerating gradient is likely around 20 MV/m with respect to peak gun fields. It
is necessary to demonstrate viable high-average-current choke joint designs and cathode
compatibility with the SRF environment, together with a lack of contamination of that
environment. As with the NCRF gun, cathode selection is an issue with the diamond
amplifier as the preferred approach and multi-alkalis as a backup. However, in contrast to
the normal-conducting gun, the SRF gun is expected to have excellent vacuum properties at
the cathode surface. At this point we must await experimental demonstration of this option
before it can be adopted as a serious candidate for near term facilities.
Finally, all the injector technology options must address field limits set by dark
current and high-power RF delivery to the accelerating cavities. While high-order modes
(HOM), wakefields and beam break up (BBU) instabilities are more issues for the ERL ring
accelerating cavities than for the injector cavities, they must still be given serious
5
consideration in the design process at high beam power. Emittance growth due to space
charge and coherent synchrotron radiation (CSR) in mergers and other beam transport
elements is also an aspect of the injector design and selection.
In the following sections, we describe the design and status of one example of each
principle injector option.
3. DC GUN AND SRF BOOSTER
The present leading candidate for high-average-current ERL injectors is a DC
photocathode gun closely coupled to an SRF booster accelerator. One such device has been
designed and fabricated by AES and is presently being assembled at JLAB for testing on
their injector test stand.
As shown in Fig.2, the device begins with a 500 kV DC gun [26] followed by an
emittance compensation solenoid [27]. The electron beam then enters the 748.5 MHz SRF
cryomodule which consists of three single cell fundamental cavities and one 2245.5 MHz
third harmonic cavity that accelerate the beam to 7 MeV. The third harmonic cavity is the
second cell in the string, whose function is to linearize the longitudinal phase space on exit
from the cryostat, as shown by the longitudinal phase space plots in the figure. As was
demonstrated with the Boeing injector [28], we have shown that the addition of the
longitudinal phase space correction cavity significantly improves the beam quality in these
injectors.
Specifically at 1 nC or 0.75 A, this configuration can deliver 5.1 microns
transverse and 43 keV-psec longitudinal rms emittance at 7 MeV, which is more than
adequate for very high-power IR FEL operation. However, due to the recent addition of the
harmonic cavity to the actual hardware, we do not list the effect of this correction for 133 pC
bunches in Tables 1 and 3, and hence better performance is expected from this device than
6
indicated. In contrast, the Cornell approach uses five 1300 MHz double-cell booster cavities
for their DC gun injector.
When every RF bucket is filled with 133 pC, the single cell device provides an
average current of 100 mA and an average electron beam power of 700 kW at the 7 MeV
injector output. The injector and power couplers have been designed to handle these power
levels. The sequence of single cell cavities provides latitude for adjusting the longitudinal
phase space through different cavity phasing and ameliorates HOM and wakefield effects
driven by high current. The use of 748.5 MHz means that the injector is compatible with the
existing JLAB ERL FEL ring although there are no present plans to install it on that device.
Fig. 3 shows four completed single-cell SRF cavities, while Fig. 4 shows the 3rd
harmonic cavity, all minus their helium vessels. Cavity cleaning has begun at JLAB with
assembly scheduled for completion by the end of 2005. The three fundamental RF power
couplers, one per cavity, are designed to deliver 350 kW each. Testing will begin at JLAB in
2006, following the completion of the injector test stand. Initial tests will demonstrate bunch
charges up to 1 nC at low PRF, due to initial RF power limitations. Later RF power upgrades
should enable 100 mA characterization in 2008.
4. NORMAL CONDUCTING RF GUN
The second high-power injector approach that is under development at AES is the
normal-conducting, CW, photocathode RF electron gun that is shown in Fig. 5. Los Alamos
performed the physics and RF design for this 700 MHz, 2½-cell, 3 nC device that delivers
100 mA at a 35 MHz PRF. Higher currents could be delivered without impacting the gun
thermal or beam properties, simply by increasing the PRF. A third full cell does not support
acceleration but rather serves as a vacuum manifold to permit very high pumping on the gun
7
during operation. The crucial issue for this concept is the extremely high-average-power and
the peak power densities that result from the resistive losses in the copper of the gun.
Two dimensional and three dimensional thermal, stress, and displacement analyses
were conducted on the gun design where the effects of temperature and pressure coupled
with the RF response were all taken into account. The thermal stresses are such that the gun
is manufactured from Glidcop®. The total thermal load of the gun is about 720 kW, but
analysis indicates the design coolant flow will adequately cool the device.
Fig. 6 shows two of the gun cells plated and ready for brazing. One of the ridge
loaded waveguide penetrations is visible on cell 3. It also shows the “dogbone” iris of the
power coupler which is a critical thermal and braze point. This gun represents one of the
most complex brazing cycles that has ever been attempted. Currently, we are 25% complete
on the braze cycle.
The gun is scheduled for delivery to Los Alamos for testing in late 2005. An existing
Los Alamos 1 MW RF test stand will be used to perform a thermal test of the gun in early
2006.
Beam tests up to about 200 mA CW could be performed in 2006 at reduced
accelerating gradient with 1 nC bunches and 200 MHz PRF using the existing LANL RF
power, once a preparation chamber and load lock are added to the gun to permit multi-alkali
cathode insertion. Addition of a booster, probably SRF and similar to that described above,
would enable achieving typical ERL injection energy and performance requirements.
5. SUPERCONDUCTING RF GUN
The final option under development at AES in collaboration with BNL, JLAB and
FZR is a high-current SRF gun. This gun is being designed and fabricated to deliver 0.5 A to
the ERL test ring that is being built at BNL [19]. This high current requires a substantial
8
departure from the present FZR 3½-cell design at 1.3 GHz [16]. Firstly, we have adopted a
½-cell gun configuration at the lower frequency of 703.75 MHz, which is compatible with
the RHIC RF frequency, in order to accommodate the higher currents, approaching 0.5 A,
required for the RHIC electron cooling rings and the e-RHIC collider. Secondly, primarily
because of thermal issues, but also for simplicity of fabrication, we determined to utilize a
quarter wave choke joint concept [29] that is different from the FZR approach. This is
shown to the left in Fig. 7 together with the ½ cell cavity. The details of the output iris and
beamtube are not finally set at this time and will change.
Thermal and stress analyses of this SRF gun with the quarter wave choke joint have
been completed. For 0.5 A operation, the thermal load on the cathode stalk, which is cooled
with liquid nitrogen, is between 150 and 180 W, depending on whether a multi-alkali or
diamond amplifier cathode is employed. Fig. 8 shows the SRF gun cryostat with a detail of
the single cell in the upper left. The cathode preparation chamber is being designed for
multi-alkali, diamond and dispenser cathodes.
This injector is presently in the final design phase. Delivery to BNL is planned for
early 2007. Initial gun performance testing will therefore be completed in 2007.
6. CONCLUSIONS
High-current ERL facilities are being proposed and constructed all over the world.
Present facilities operating at the 10’s of mA level will give way to 100 mA and higher
current devices. Three technology options exist for the high-current electron injectors these
ERL facilities will need.
DC guns with SRF boosters are a relatively mature approach and suitable for nearterm deployment. They will likely deliver the required performance at the 100 mA current
level and should permit extrapolation towards the Ampere-level. Further, the cathode issue
9
is largely solved for this technology at the 100 mA current level with the use of GaAs,
although extending the time between recesiations is important. The achievable DC gun
accelerating gradient, perhaps limited by dark current, needs to be determined.
Normal-conducting RF injectors are the least attractive option for CW operation
because of their inefficiency due to resistive wall losses. The achievable gradient is also
limited by the resulting thermal constraints. Multi-alkalis are the cathode of choice but
suitable lifetime and reliability have yet to be demonstrated. Nevertheless, the Boeing gun,
at 32 mA CW, is still the state-of-the-art for high-average current injectors and serves as a
proof-of-concept for 100 mA operation. If the cathode, thermal and power coupling issues
are solved, these guns can deliver Ampere-level performance and they also remain attractive
for lower PRF high-brightness applications as indicated in Table 1 for 4GLS.
Superconducting RF injectors are the least mature option and unproven at highaverage current. However, they are the most desirable approach since, in principle, they
deliver the better RF gun beam performance at DC gun efficiency levels. They also promise
the highest accelerating gradient and thus the most compact option, but must demonstrate a
compatible cathode technology and high RF power handling.
The performance of three distinct high-current ERL injector technologies, which are
under development at AES in partnership with National Laboratories, is listed in Table 3.
The impact of harmonic correction, which is important for each technology, is shown in
parentheses only for the SRF gun, and each requires further beam tailoring for ERL merging.
The 100 mA DC gun with an SRF booster is presently being assembled at JLAB for testing
in 2007. The normal-conducting gun is in fabrication for delivery to LANL in late 2005. It
will undergo thermal testing equivalent to beam operation at 1 A in 2006. Finally, the SRF
gun, which will be installed on the BNL test ERL is in final design. Operation testing of this
gun to 0.5 A will occur in 2007.
10
ACKNOWLEDGEMENTS
The AES injector work is supported by the Naval Sea Systems Command, the Office
of Naval Research, the DOD Joint Technology Office and the Missile Defense Agency.
We gratefully acknowledge the contributions of the following individuals to the
material presented: A. Ambrosio, H. Bluem, V. Christina, M. D. Cole, M. Falletta, D.
Holmes, E. Peterson, J. Rathke, T. Schultheiss and R. Wong of AES to the three AES
injectors; S. Benson, E. Daly, D. Douglas, F. Dylla, W. Funk, C. Hernandez-Garcia, J.
Hogan, P. Kneisel, J. Mammosser, G. R. Neil, L. Phillips, J. Preble, R. Rimmer, C. Rode, T.
Siggins, T. Whitlach, M. Wiseman of JLAB, R. Campisi of ORNL, and J. Sekutowicz of
DESY to the AES/JLAB DC Gun and Booster; I. Ben-Zvi, A. Burrill, R. Calaga, P.
Cameron, X. Chang, H. Hahn, D. Kayran, J. Kewisch, V. Litvinenko, G. McIntyre, A.
Nicoletti, J. Rank, J. Scaduto, T. Srinivasan-Rao, K. Wu, A. Zaltsman, Y. Zhao of BNL, D.
Janssen of FZR, J. W. Lewellen of ANL, L. Phillips, J. Preble of JLAB, and V. NguyenTuong of Tunnel Dust, to the AES/BNL SRF Gun; P. Colestock, J. P. Kelley, S. Kurennoy,
D. Nguyen, S. Russell, W. Reass, D. Rees, D. Schrage, R. Wood of LANL and L. Young of
TechSource to the LANL/AES NCRF Gun.
Additionally, we wish to thank D. Dowell of LCLS and J. Adamski of Boeing (the
Boeing injector and Figure 1), C. Sinclair of Cornell University (the Cornell ERL), R.
Rimmer of JLAB (LUX), E. Seddon and M. Dykes of ASTeC, Daresbury, UK (4GLS), N.
Vinokurov of BINP, Russia (BINP Recuperator) and E. Minehara of JAERI, Japan (JAERI
FEL) for graciously providing information on their described ERL and injector projects.
11
FIGURE CAPTIONS
Figure 1. 433 MHz, 32 mA Boeing NCRF injector.
Figure 2. DC Gun and SRF booster (upper left) with fundamental cavity (upper right).
Booster with 3rd harmonic cavity showing evolution of longitudinal emittance (lower - the
vertical scale varies for each phase space plot).
Figure 3. Four 748.5 MHz SRF fundamental cavities.
Figure 4. 2245.5 MHz third harmonic SRF cavity.
Figure 5. Normal-conducting 2½-cell CW RF gun.
Figure 6. NCRF gun cell 2 (upper left) and cell 3 (upper right) plated and ready for brazing.
Waveguide irises machined and ready for plating (lower).
Figure 7. SRF gun choke joint and ½ cell cavity.
Figure 8. SRF gun cryostat with ½ cell cavity detail (upper left).
TABLE CAPTIONS
Table 1: Summary of parameters for high-current injectors and ERLs.
Table 2: ERL injector nominal values and range.
Table 3: AES ERL injector parameters.
12
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15
USA,
Figure 1
16
2245.5 MHz
3rd Harmonic SRF Cell
With RF W/G Feed
(not shown)
Spaceframe
Cold
Box
DC
Gun
Cold
Box
750 MHz
Fundamental
SRF Cells
Helium
Vessel
18
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17.6
17.4
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4
3.9 5
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1.73
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1.71
1.69
1.67
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49
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580.6 580.8
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51
z (cm)
Figure 2
17
134
13 5
172.5
173
173.5
174
174.5
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581
581.2 581.4 581.6 581.8
582
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18
Figure 4
19
Vacuum
Vacuum Pumps
Pumps
Vacuum
Chamber
with Pumps
Bucking
Solenoid
Magnet
Cathode
Backplate
Cooling
Focusing Solenoid Magnet
Figure 5
20
Ridge
Loaded
Waveguide
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21
SuperFish File Gun 6cm Iris F = 703.79036 MHz
18
18
16
16
Iris diameter = 120 mm
Beampipe diameter = 190 mm
Frequency = 703.79036 MHz
14
14
12
12
10
10
8
8
6
6
4
4
2
2
0
0
0
5
10
15
20
C:\DOCUMENTS AND SETTINGS\KAYRAN\MY DOCUMENTS\ERL\SCGUN_DESIGN\FROM_RAM\RGUN519.AM 4-28-2005 15:18:00
Figure 7
22
25
Internal
Helium
Dewar
Top Cover with Facilities
Feedthrough
Beam
Line
Isolation
Valve
Cathode Isolation Valve
Cathode
Installation
Assembly
Cavity
Assembly
Magnetic
and
Thermal
Shielding
Adjustable Supports
Vacuum Vessel
Power
Couplers
Figure 8
23
Beam
Tube
with
HOM
RF
Pickup
DEVICE
JLAB
AES/JLAB
PARAMETER
ERL FEL
Injector
DC
DC
Gun Type
Injector and ERL
RF Frequency (MHz)
1497
748.5
PRF (MHz)
74.85
748.5
Charge/Bunch (nC)
0.133
0.133
Current (mA)
10
100
Injector Energy (MeV)
7
7
Transverse rms Normalized Emittance (µm)
< 7 (7)
1.2
Longitudinal rms Emittance (keV-psec)
17 (80)
44
RMS Bunch Length (psec)
3.2 (0.35)
6.3
RMS Energy Spread (%)
0.1 (0.13)
0.5
ERLP Energy (MeV)
160
N/A
ERL Energy Goal (MeV)
200
N/A
Electron Gun
DC Gun Voltage (kV)
350
500
Gun Accelerating Field (MV/m)
4
7
Cathode Material
GaAs
GaAs
Drive Laser FWHM Pulse Length (psec)
44
44
Laser Wavelength (nm)
527
527
Laser Power at 5% QE (W)
0.5
5
Booster (DC) or Gun (RF)
Booster or Gun Type
SRF
SRF
Geometry (Cavities x Cells)
2x5
4x1
Couplers per Cavity / Type
1 / WG
1/CX:1/WG
Coupler Power (kW)
50
350
Status
Operational
Assembly
(Explanation)
(At Wiggler)
Cornell
ERL
DC
Daresbury
ERLP
DC
JAERI
ERL
DC
BINP
ERL FEL
DC
Boeing
Injector
NCRF
LANL/AES
Gun
NCRF
LUX
Gun
NCRF
AES/BNL
Gun/ERL
SRF
4GLS
ERL
SRF(NCRF)
1300
1300
0.077
100
5 - 15
< 1.0
21
2.0
0.12
100
5000
1300
81.25
0.080
6.5
8.35
1.5
13.3
4.0
0.24
35
35
499.8
10.41 (83.3)
0.5
5 (40)
2.5
30
180
11.2 (90)
1.7
20 (150)
2
32 (15)
433
27
4.75
32(132 Peak)
5
~7
700
33.3 (350)
3.0
100 (1050)
2.5
6
145
1300
1300
1.0
1300
1300
1300 (0.001)
0.080 (1.0)
100 (0.001)
10 (150)
0.5
50
<1
12.8 (14)
40
~3
N/A
N/A
0.5
N/A
N/A
703.75
351.88
1.4
500
2
2.1 / 2.8
64 (19)
15.4
3.1 (2.1)
20
40
500 - 750
8
GaAs
30
527
5
350
4
GaAs
20
527
0.325
N/A
N/A
7/7/5
Multi-Alkali
16
527
5 (53)
N/A
20
Dia./M-Alk.
TBD
527
0.2 / 25
N/A
25 (TBD)
Dia./M-Alk.
10
527
5 (~0)
SRF
5x2
2 / CX
50
Fabrication
SRF
2x9
2 / WG
SRF
2x1
Fabrication
Operational
(Upgrade)
17
230
Thermionic
N/A
N/A
N/A
Table 1
24
300
1
Thermionic
N/A
N/A
N/A
CsKSb
53
527
NCRF
N/A
N/A
3x1
1 x 1.5+1 x 3
1 x 2.5
1 / CX
2 / WG
2 / WG
50 (200)
500
Operational
Retired
Fabrication
(Upgrade) (Macropulse) (High PRF)
N/A
N/A
N/A
20 / 13 / 13
TBD
N/A
1 x 2.5
3 / WG
Analysis
600 (1000)
N/A
N/A
1 x 0.5
1 x 3.5 (TBD)
2 / CX
TBD
500
TBD
Design/Fab
Analysis
(Correction) (Low PRF)
Parameter
Value
Output Energy (MeV)
CW Average Current (mA)
Bunch Charge (nC)
Transverse rms Normalized Emittance (µm)
Longitudinal rms Emittance (keV-psec)
Bunch Length (psec)
Energy spread (%) at Injection
RF Frequency (MHz)
RF Feedthrough Power (kW)
Photocathode Frequency Response
Table 2
25
Nominal
~7
~ 200
~ 0.5
~ 1.5
< 45
~4
< 0.5
~ 700
< 500
Visible
Range
2 – 15
100 – 500
0.075 - 3
<1-6
25 - 145
2-7
0.1 - 0.5
500 - 1300
50 - 500
Visible
DEVICE
PARAMETER
Gun Type
RF Frequency (MHz)
PRF (MHz)
Charge/Bunch (nC)
Current (mA)
Injector Energy (MeV)
Mean Accelerating Gradient (MV/m)
Transverse rms Normalized Emittance (µm)
Longitudinal rms Emittance (keV-psec)
RMS Bunch Length (psec)
RMS Energy Spread (%)
AES/JLAB
Injector
DC
748.5
748.5
0.133
100
7
7 / 13.5
1.2
44
6.3
0.5
Table 3
26
LANL/AES
Gun
NCRF
700
33.3
3.0
100
2.5
7
6
145
0.5
AES/BNL
Gun/ERL
SRF
703.75
351.88
1.4
500
2
23.5
2.5
64 (19)
15.4
2.1 (1.7)