Use of electrostatic gridded lenses in the laser ion source at CERN
The GEL LEBT provides high efficiency beam transport and matching to the RFQ acceptance in the 4-dimensional phase space. The rms emittance growth is relatively small even for 60 kV extraction voltage. The number of particles occupying the 4-D RFQ acceptance strongly depends from the beam emittance...
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Національний науковий центр «Харківський фізико-технічний інститут» НАН України
1999
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| Series: | Вопросы атомной науки и техники |
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| Cite this: | Use of electrostatic gridded lenses in the laser ion source at CERN / V. Derbilov, P. Ostroumov, H. Kugler, N. Lisi, C. Meyer, R. Scrivens // Вопросы атомной науки и техники. — 1999. — № 3. — С. 33-35. — Бібліогр.: 4 назв. — англ. |
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irk-123456789-811492015-05-31T17:20:05Z Use of electrostatic gridded lenses in the laser ion source at CERN Derbilov, V.I. Ostroumov, P.N. Kugler, H. Lisi, N. Meyer, C. Scrivens, R. The GEL LEBT provides high efficiency beam transport and matching to the RFQ acceptance in the 4-dimensional phase space. The rms emittance growth is relatively small even for 60 kV extraction voltage. The number of particles occupying the 4-D RFQ acceptance strongly depends from the beam emittance at the entrance of the GEL LEBT. In most realistic case with the input emittance equal to the measured one, which is 320 p×mm×mrad (4×rms emittance) the number of particles inside the 4-D space with the projection emittance of 200 p×mm×mrad is 38% at the entrance and 35% at the output of GEL LEBT, which means that LEBT does not practically destroy beam emittance. The experimental value of the yield to the double aperture is 35% and confirms the expected performance of the GEL LEBT. 1999 Article Use of electrostatic gridded lenses in the laser ion source at CERN / V. Derbilov, P. Ostroumov, H. Kugler, N. Lisi, C. Meyer, R. Scrivens // Вопросы атомной науки и техники. — 1999. — № 3. — С. 33-35. — Бібліогр.: 4 назв. — англ. 1562-6016 http://dspace.nbuv.gov.ua/handle/123456789/81149 en Вопросы атомной науки и техники Національний науковий центр «Харківський фізико-технічний інститут» НАН України |
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The GEL LEBT provides high efficiency beam transport and matching to the RFQ acceptance in the 4-dimensional phase space. The rms emittance growth is relatively small even for 60 kV extraction voltage. The number of particles occupying the 4-D RFQ acceptance strongly depends from the beam emittance at the entrance of the GEL LEBT. In most realistic case with the input emittance equal to the measured one, which is 320 p×mm×mrad (4×rms emittance) the number of particles inside the 4-D space with the projection emittance of 200 p×mm×mrad is 38% at the entrance and 35% at the output of GEL LEBT, which means that LEBT does not practically destroy beam emittance. The experimental value of the yield to the double aperture is 35% and confirms the expected performance of the GEL LEBT. |
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Derbilov, V.I. Ostroumov, P.N. Kugler, H. Lisi, N. Meyer, C. Scrivens, R. |
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Derbilov, V.I. Ostroumov, P.N. Kugler, H. Lisi, N. Meyer, C. Scrivens, R. Use of electrostatic gridded lenses in the laser ion source at CERN Вопросы атомной науки и техники |
| author_facet |
Derbilov, V.I. Ostroumov, P.N. Kugler, H. Lisi, N. Meyer, C. Scrivens, R. |
| author_sort |
Derbilov, V.I. |
| title |
Use of electrostatic gridded lenses in the laser ion source at CERN |
| title_short |
Use of electrostatic gridded lenses in the laser ion source at CERN |
| title_full |
Use of electrostatic gridded lenses in the laser ion source at CERN |
| title_fullStr |
Use of electrostatic gridded lenses in the laser ion source at CERN |
| title_full_unstemmed |
Use of electrostatic gridded lenses in the laser ion source at CERN |
| title_sort |
use of electrostatic gridded lenses in the laser ion source at cern |
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Національний науковий центр «Харківський фізико-технічний інститут» НАН України |
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1999 |
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http://dspace.nbuv.gov.ua/handle/123456789/81149 |
| citation_txt |
Use of electrostatic gridded lenses in the laser ion source at CERN / V. Derbilov, P. Ostroumov, H. Kugler, N. Lisi, C. Meyer, R. Scrivens // Вопросы атомной науки и техники. — 1999. — № 3. — С. 33-35. — Бібліогр.: 4 назв. — англ. |
| series |
Вопросы атомной науки и техники |
| work_keys_str_mv |
AT derbilovvi useofelectrostaticgriddedlensesinthelaserionsourceatcern AT ostroumovpn useofelectrostaticgriddedlensesinthelaserionsourceatcern AT kuglerh useofelectrostaticgriddedlensesinthelaserionsourceatcern AT lisin useofelectrostaticgriddedlensesinthelaserionsourceatcern AT meyerc useofelectrostaticgriddedlensesinthelaserionsourceatcern AT scrivensr useofelectrostaticgriddedlensesinthelaserionsourceatcern |
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2025-07-06T05:28:41Z |
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2025-07-06T05:28:41Z |
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1836874175583617024 |
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USE OF ELECTROSTATIC GRIDDED LENSES IN THE LASER ION
SOURCE AT CERN
V.Derbilov, P.Ostroumov; H.Kugler*, N.Lisi*, C.Meyer*, R.Scrivens*
INR RAS, Moscow, Russia; *CERN, Geneva, CH
For the transport and focusing of the LIS 60
kV and 60 mA multi-charge beam to the acceptance of
the RFQ the gridded electrostatic lenses (GEL) have
been proposed. Main features of the gridded lenses are:
• Simple and cheap performance;
• Stronger focusing in comparison with solenoids or
standard Einzel lenses [1];
• There is no any type of aberrations (no aberrations
have been observed in simulation of relatively large
emittances ~200–320 π⋅mm⋅mrad).
• The secondary electrons are removed from the ion
beam occupation area, it must help to stable transport of
ion beam through LEBT.
As a grid the W-Re wires with 50 µm diameter
have been used. The grid has been designed as a
rectangular net of wires with 4 mm and 3 mm inter-wire
space. Four-grid GEL system has a transparency of
94%. The own grid does not produce any emittance
growth. As follows from the simulation an emittance
growth occurs for a beam with very low emittance ~ 30
π⋅mm⋅mrad (unnormalised, 60 kV).
Another phenomena such as a heating of the wires
and sputtering of the wire material can be neglected due
to very low average intensity of the ion beam.
Estimation of sputtering rate by available empirical
formulas [2] shows that 10 µm wire material can be
sputtered during 8500 hours of operation with the ion
flow 1010 atoms/(sec⋅cm2).
The LEBT containing 4 electrostatic lenses has
been proposed and studied by the CPO code [3].
Simulation of GEL LEBT has been done with 3 values
of the input emittances, shown in Tables 1 and 2.
Table 1
INPUT OF GEL
1 2 3
4 rms emittance, π⋅mm⋅mrad 128 204 320
Total emittance, π⋅mm⋅mrad 200 320 500
Number of particles inside 2D
emittance 200 π⋅mm⋅mrad
100% 88% 67%
Number of particles inside 4D
emittance with projections 200
π⋅mm⋅mrad
100% 75% 38%
Table 2
OUTPUT OF GEL
4 rms emittance, π⋅mm⋅mrad 228 328 488
RMS emittance growth factor 1.78 1.61 1.53
Number of particles inside
2D emittance 200 π⋅mm⋅mrad
82% 76% 52%
Number of particles inside
4D emittance with projections
200 π⋅mm⋅mrad
71% 62% 35%
Fig.1. Beam envelope in GEL LEBT. V1=7 kV, V2=26
kV, V3=36 kV. Einput, total =500 π⋅mm⋅mrad. Einput, 4rms =
320 π⋅mm⋅mrad. Mesh size =1mm, Total number of
particles (taking into account symmetry planes) =2400.
I beam=60 mA, Uextraction=60 kV.
Ein=500 pi mm mrad, Input emittance
I=60 mA, U=60kV
-0.2
-0.15
-0.1
-0.05
0
0.05
0.1
0.15
0.2
-20 -16 -12 -8 -4 0 4 8 12 16 20
x, mm
dx
/d
z,
ra
d
Fig. 2. Input distribution of 60 mA beam, Etotal=500 π⋅
mm⋅mrad, 4⋅Erms=320 π⋅mm⋅mrad.
Ein=500 pi mm mrad, V=7,26,36 kV,
I=60 mA, U=60kV
-0.3
-0.2
-0.1
0
0.1
0.2
0.3
-10 -8 -6 -4 -2 0 2 4 6 8 10
x, mm
dx
/d
z,
ra
d
Fig. 3. Phase space plot in the entrance of the RFQ. The
RFQ acceptance is shown. The total number of particles
inside 4-dimensional phase space with 200 π⋅mm⋅mrad
emittances in xx′ and yy′ is 35%.
Fig. 1-3 show the beam envelopes along the GEL
LEBT, initial and output phase space plots. The
simulations have been done using 600 particles and 2
symmetry planes: x=0 and y=0. Mesh size for space
charge calculations was 1 mm. The simulation time with
7 iterations is ~8 hours (at 200 MHz PC) and depends
on the initial emittance.
SENSITIVITY OF THE GEL LEBT TO CURRENT
VARIATION
For the initial total beam emittance 500 π⋅mm⋅
mrad (case 3 in Table 1) the input current has been
changed to 45 mA and 30 mA. Simulation has been
done with the voltage setting shown in Fig. 1. As
expected the yield of beam current drops as beam
current is decreased because the voltage setting is
optimized for the 60 mA beam current (see Fig. 4). The
ВОПРОСЫ АТОМНОЙ НАУКИ И ТЕХНИКИ. 1999. №3.
Серия: Ядерно-физические исследования (34), с. 33-35.
33
corresponding phase space plot for 45 mA beam is
shown in Fig. 5.
0
10
20
30
40
50
20 30 40 50 60 70
I, mA
Y
ie
ld
, %
1
1.2
1.4
1.6
1.8
2
20 30 40 50 60 70
I, mA
R
M
S
e
m
itt
an
ce
g
ro
w
th
fa
ct
or
Fig. 4. Current yield into the 4D RFQ acceptance (left)
and rms emittance growth factor (right) as a function of
beam current. The voltage setting is optimised for
60 mA beam.
Ein=500 pi mm mrad, V=7,26,36 kV,
I=45 mA, U=60kV
-0.3
-0.2
-0.1
0
0.1
0.2
0.3
-10 -8 -6 -4 -2 0 2 4 6 8 10
x, mm
dx
/d
z,
ra
d
Fig. 5. Phase space plot in the entrance of the RFQ for
45 mA beam. The RFQ acceptance is shown. The total
number of particles inside 4-dimensional phase space
with 200 π⋅mm⋅mrad emittances in xx′ and yy′ is 31%.
MECHANICAL DESIGN
Fig. 6. Schematic view of the electrodes.
1 – electrode, 2 – isolator, 3 – grid.
The mechanical layout of the GEL is shown in Fig.
6 and 7. High voltage to the electrodes is supplied
through the feedthroughs 4 (Fig. 7). The electrodes are
isolated in vacuum by the shaped rods 2. The wires are
mounted on aluminium support. The positive voltage is
applied to the electrodes shown in Fig. 6 and 7.
Fig. 7. General assembly drawings of the GEL LEBT.
4 – 50 kV HV feedthrough.
In this case the grids are grounded. However the
electrode system with negative voltage on the grids can
be used for the focusing too. The assembly drawings of
such electrodes are shown in Fig. 8. The latter has better
focusing properties because the focusing effect occurs
with the acceleration of the beam. In addition the
number of grids can be less than in the GEL shown in
Fig. 6. However the disadvantage of such system is a
production of some electrons which can reach the ion
source, also the focusing voltage is higher. Both systems
have been tested in the experiments. But main studies
have been carried out with the system shown in
Fig. 6, 7.
Fig. 8. General assembly drawings of the GEL LEBT.
An average current of 40 mA (for solenoid LEBTs
it was 17 mA [4]) has been observed in the Faraday cup
of φ = 6.5 mm. The source current was then 70 mA.
Inserting the double aperture device gave a yield of
30 %. Near the focal plane, emittance measurements
confirmed the predicted low emittance growth. The
typical emittance of the extracted ion beam downstream
of the GEL LEBT is shown in Fig. 9. In recent
experiments the yield to the double aperture Faraday
cup has been increased up to 35%.
ВОПРОСЫ АТОМНОЙ НАУКИ И ТЕХНИКИ. 1999. №3.
Серия: Ядерно-физические исследования (34), с. 33-35.
34
-1
8
-1
2 -6 0 6 12 18
-160.4
-143.2
-125.9
-108.6
-91.4
-74.1
-56.8
-39.6
-22.3
-5.0
12.2
29.5
46.8
64.0
81.3
98.6
115.8
133.1
150.4
167.6
X, mm
X', mrad
160-180
140-160
120-140
100-120
80-100
60-80
40-60
20-40
0-20
Voltage set: 7,30, 15 kV
4*Erms=453 π mm mrad
Fig. 9. Transverse emittance output of the GEL.
CONCLUSION
The GEL LEBT provides high efficiency beam
transport and matching to the RFQ acceptance in the 4-
dimensional phase space. The rms emittance growth is
relatively small even for 60 kV extraction voltage. The
number of particles occupying the 4-D RFQ acceptance
strongly depends from the beam emittance at the
entrance of the GEL LEBT. In most realistic case with
the input emittance equal to the measured one, which is
320 π⋅mm⋅mrad (4⋅rms emittance) the number of
particles inside the 4-D space with the projection
emittance of 200 π⋅mm⋅mrad is 38% at the entrance and
35% at the output of GEL LEBT, which means that
LEBT does not practically destroy beam emittance. The
experimental value of the yield to the double aperture is
35% and confirms the expected performance of the GEL
LEBT.
REFERENCES
1. P.A. Sturrock. Static and Dynamic Electron Optics.
Cambridge, 1955.
2. M.D. Gabovich et al. Ion and Atom Beams for
nuclear fusion and technology. Moscow,
Energoatomizdat. 1986 (in Russian).
3. P.N. Ostroumov. LIS LEBT on the base of
electrostatic gridded lenses. PS/HP/Note 99-04
(Tech.).
4. P. Fournier et al. CERN PS Laser Ion Source
Development. Paper presented to PAC99, New-
York, March 1999.
35
Input of GEL
Output of GEL
MECHANICAL DESIGN
CONCLUSION
REFERENCES
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