Nanosecond diagnostics of proton beam current impulse with wall current monitor on MMF LINAC
The described device now operates at the MMF H+ beam transport line. A number of physics experiments with pulse neutron sources have been done successfully. The design of such a device for the MMF H- beam transport line is needed.
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| Veröffentlicht in: | Вопросы атомной науки и техники |
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| Datum: | 1999 |
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Національний науковий центр «Харківський фізико-технічний інститут» НАН України
1999
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| Zitieren: | Nanosecond diagnostics of proton beam current impulse with wall current monitor on MMF LINAC / A.A. Men’shov, A.V. Novikov-Borodin, Y. Yin // Вопросы атомной науки и техники. — 1999. — № 3. — С. 66-67. — Бібліогр.: 4 назв. — англ. |
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Digital Library of Periodicals of National Academy of Sciences of Ukraine| _version_ | 1859625783659593728 |
|---|---|
| author | Men’shov, A.A. Novikov-Borodin, A.V. Yin, Y. |
| author_facet | Men’shov, A.A. Novikov-Borodin, A.V. Yin, Y. |
| citation_txt | Nanosecond diagnostics of proton beam current impulse with wall current monitor on MMF LINAC / A.A. Men’shov, A.V. Novikov-Borodin, Y. Yin // Вопросы атомной науки и техники. — 1999. — № 3. — С. 66-67. — Бібліогр.: 4 назв. — англ. |
| collection | DSpace DC |
| container_title | Вопросы атомной науки и техники |
| description | The described device now operates at the MMF H+ beam transport line. A number of physics experiments with pulse neutron sources have been done successfully. The design of such a device for the MMF H- beam transport line is needed.
|
| first_indexed | 2025-11-29T11:42:33Z |
| format | Article |
| fulltext |
NANOSECOND DIAGNOSTICS OF PROTON BEAM CURRENT
IMPULSE WITH WALL CURRENT MONITOR ON MMF LINAC
Men'shov A.A., Novikov-Borodin A.V. Yin Y.*
Institute for Nuclear Reseach of RAS, 117312 Moscow Russia,*TRIUMF, Vancouver Canada
Nanosecond pulse creation of proton beam
current on the Moscow meson factory linear accelerator
is necessary for neutron physics experiments and the
storage ring operation. The diagnostics of such pulse
with a few nanoseconds rise and fall times and with a
pulse length from few nanoseconds to few
microseconds is needed. The Wall Current Monitor
(WCM) applied for this purpose in the 400 keV linac
beam transport line is described. The WCM bandwidth
is from 20 kHz to 1 GHz. The Wall-Current monitor
being used now at the MMF Linac's beam transport
channel is described. The test structure, experimental
results and the construction of the operational device are
presented, the method of the precise injector energy
measurements are discussed.
INTRODUCTION
Measuring beam parameters after an injector is
very important task for accelerator commissioning,
particularly while using the beam of micropulse regime
for neutron experiments. It is necessary to control beam
parameters directly behind the chopper [1, 2] that is a
basic device for creating the micropulse regime at the
MMF Linac. To measure the continuous proton beam
pulse with the length from 0.2 to 1.0 µs and rise and fall
times less than 10 ns one need to create the detector
with a wide frequency range from ~20 kHz to 1 GHz.
Also good matching and shielding are needed for the
device operating in a very high noise level conditions.
The Wall-Current Monitor was created for these
measurements.
1. THE TEST WALL-CURRENT MONITOR
Fig.1 Simplified equivalent circuit of the Wall Current
Monitor
400 keV H+ beam micropulses created by the
chopper during the accelerator operation for physics
experiments were used. The micropulses from 200 ns to
1.0 µs are usually used and are needed as small rise and
fall times as possible. Now ~20 ns is available with the
chopper. The pulse beam current on the beam transport
channel is about 60 mA.
Specially designed test equipment was created to
check the required parameters for the WCM. The
simplified WCM equivalent circuit [3] is shown in
Fig. 1.
The corresponding frequency response of the
WCM will be:
( ) ( )
( )
LjRCjI
VZ
ωωω
ωω
11
1
++
== (1)
Analyzing this expression one can conclude that
the time constant τ c RC= is corresponding to the high
frequency response and τ L L R= / to the low one.
Usually the gap resistance R is about 1 Ohm. As
far as the capacitance across the gap is about C = 30÷
40 pF, the high frequency cut off is calculated to be 1/2
πRC = 5 GHz. The low frequency cut off of a
conventional type is higher than the required one to
observe the Linac beam pulse that continues for few
microseconds. Increasing the inductance of the WCM is
necessary for decreasing the low frequency cut off.
Fig.2 Wall Current Monitor test bench.
The WCM test bench scheme is presented in
Fig.2. Two commercial 50 Ohm matching structures are
divided by the ceramic ring and connected with 100 x
110 Ohm resistor over the perimeter of the ceramic ring.
The square wave-form oscillator represents the beam
current pulse. Up to six permalloy tape rings and up to
four wire shielding rings were used to investigate the
dependence of the WCM low frequency cut off. The
corresponding experimental results are presented in
Fig.3. Figures over the curves show the number of
permalloy rings during the experiment and the number
of the wire shielding rings are in brackets.
Fig.3 Test WCM responce
From (1), taking into account that cL ττ 〉 〉 , one
can estimate the flat voltage droop ∆U during the time ∆
t as:
ВОПРОСЫ АТОМНОЙ НАУКИ И ТЕХНИКИ. 1999. №3.
Серия: Ядерно-физические исследования. (34), с. 66-67.
66
∆−−=∆
L
tUU
τ
exp1max . (2)
The corresponding time constants recalculated
by (2) will be the following ones.
For four wire shielding rings without permalloy
rings τ = 0,23 µs, for one wire shielding ring without
permalloy rings τ = 0,64 µs, for one permalloy ring
τ = 5,93 µs, for three permalloy rings τ = 10,95 µs, for
six permalloy rings τ = 19,67 µs.
2. MMF H+, H- TRANSPORT LINE
Fig.4. Schematic diagram of H+, H- beam transport line.
The schematic diagram of the MMF H+, H- beam
transport line is illustrated in Fig.4.
The chopper is placed directly behind the
injector in the first part of the beam transport line to
protect transport line equipment and especially
diagnostic equipment having a direct contact with the
beam from a damage during an accelerator
commissioning. The charged particle beam current at
the MMF first part beam transport line represents the ∼
150 µs 200 mA pulse train with 50 Hz (it will be
increased up to 100 Hz soon) pulse repetition rate. The
injected beam unnormalized emittance is 8-10 π cm
mrad, its cross diameter is about 5 cm. For MMF
Chopper commissioning and a beam microstructure
control a special wideband Wall Current monitor was
designed and placed at the second part of the beam
transport line. Using this device on the second part is
conditioned on a cleaning effect of the bending magnet.
Bending magnets operate like a particle separator so
undesirable ions flowing from the injector are reduced.
To measure the continuous proton beam pulses
with a pulse duration up to 5.0 µs and pulse edges about
20 ns we used WCM with a frequency range from
20 kHz to 3 GHz. An experimental shape of the
chopped beam current pulse is shown in Fig.5. The dash
line points to a shape of tail beam current pulses that
appear together with a single pulse (solid line) due to
reflected waves existence if no matching circuit is used.
Fig.5 WCM signal from H+ beam.
However, the wall-current monitor does not let to
measure an absolute beam current amplitude because of
its frequency dependence. This estimation can be made
with the help of neutron beam loss monitors or by
means of a Faraday cup signal integration. Knowing the
shape and the amplitude of a full beam current
macropulse as well as the shape of a chopped one (from
wall-current monitor) and analyzing the values of loss
monitors or a Faraday cup in both cases, one can
estimate a correlation between full and chopped beam
current amplitudes. The corresponding calculations
show that a chopped beam current amplitude is at least
95% of a full one.
3. ENERGY MEASUREMENTS
With the help of two WCM it is possible to
measure the absolute energy of the injector beam by
measuring the time shift between signals. The block
diagram of these measurements is shown in Fig.6. Here
l is the known distance between two WCMs, t1 (t2) is the
time that is taken by signal to go from WCM1 (WCM2)
to the time shift measuring device and ∆t3 is a device
systematic error. If we can measure the time signal shift,
it is possible to determine the beam velocity as βc = l/∆
t, where c is the velocity of light. By means of the
following approach it is possible to determine the
absolute time shift ∆t between two WCMs.
Fig.6 Energy measurement block diagram
Let ∆t'1 is the time shift measured by the device.
Replacing the cables between WCMs as shown in Fig.6
we can get ∆t'2. These time shifts may be expressed as:
∆t'1 = ∆t + t2 + ∆t3 – t1, (3)
∆t'2 = ∆t + t1 - ∆t3 – t2 .
So, from here one can get the absolute time shift:
∆t = (∆t'1 + ∆t'2 )/2. (4)
Usually, it is not necessary to do this procedure every
time you want to measure the beam energy. It is enough
to determine the correction ∆ = (∆t'1 - ∆t'2 )/2 once.
Finally, one can measure the absolute time shift as:
∆t = ∆t'1 - ∆. (5)
ВОПРОСЫ АТОМНОЙ НАУКИ И ТЕХНИКИ. 1999. №3.
Серия: Ядерно-физические исследования. (34), с. 66-67.
66
The accuracy of the measurements mainly will be
defined by the noise conditions.
CONCLUSION
The described device now operates at the MMF
H+ beam transport line. A number of physics
experiments with pulse neutron sources have been done
successfully. The design of such a device for the MMF
H- beam transport line is needed.
REFERENCES
1. Novikov A.V. et al, Proc. of PAC97, vol.3,
Vancouver, Canada, 1997, p. 2732.
2. Novikov A.V. et al, XIV Accel.Conf., Protvino, v.1,
1994 (in Russian).
3. Yin Y. TRI-DN-90-K144, TRIUMF, Canada, 1990.
4. Nakagawa H. et.al, IEEE Trans., NS-26, No.3, June
1979, pp.3367-3369.
ВОПРОСЫ АТОМНОЙ НАУКИ И ТЕХНИКИ. 1999. №3.
Серия: Ядерно-физические исследования. (34), с. 66-67.
66
Introduction
1. The test wall-current monitor
3. ENERGY MEASUREMENTS
Conclusion
References
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| id | nasplib_isofts_kiev_ua-123456789-81377 |
| institution | Digital Library of Periodicals of National Academy of Sciences of Ukraine |
| issn | 1562-6016 |
| language | English |
| last_indexed | 2025-11-29T11:42:33Z |
| publishDate | 1999 |
| publisher | Національний науковий центр «Харківський фізико-технічний інститут» НАН України |
| record_format | dspace |
| spelling | Men’shov, A.A. Novikov-Borodin, A.V. Yin, Y. 2015-05-14T21:04:46Z 2015-05-14T21:04:46Z 1999 Nanosecond diagnostics of proton beam current impulse with wall current monitor on MMF LINAC / A.A. Men’shov, A.V. Novikov-Borodin, Y. Yin // Вопросы атомной науки и техники. — 1999. — № 3. — С. 66-67. — Бібліогр.: 4 назв. — англ. 1562-6016 https://nasplib.isofts.kiev.ua/handle/123456789/81377 The described device now operates at the MMF H+ beam transport line. A number of physics experiments with pulse neutron sources have been done successfully. The design of such a device for the MMF H- beam transport line is needed. en Національний науковий центр «Харківський фізико-технічний інститут» НАН України Вопросы атомной науки и техники Nanosecond diagnostics of proton beam current impulse with wall current monitor on MMF LINAC Наносекундная диагностика импульсов пучка протонов с помощью датчика стеночного тока на ЛУ ММФ Article published earlier |
| spellingShingle | Nanosecond diagnostics of proton beam current impulse with wall current monitor on MMF LINAC Men’shov, A.A. Novikov-Borodin, A.V. Yin, Y. |
| title | Nanosecond diagnostics of proton beam current impulse with wall current monitor on MMF LINAC |
| title_alt | Наносекундная диагностика импульсов пучка протонов с помощью датчика стеночного тока на ЛУ ММФ |
| title_full | Nanosecond diagnostics of proton beam current impulse with wall current monitor on MMF LINAC |
| title_fullStr | Nanosecond diagnostics of proton beam current impulse with wall current monitor on MMF LINAC |
| title_full_unstemmed | Nanosecond diagnostics of proton beam current impulse with wall current monitor on MMF LINAC |
| title_short | Nanosecond diagnostics of proton beam current impulse with wall current monitor on MMF LINAC |
| title_sort | nanosecond diagnostics of proton beam current impulse with wall current monitor on mmf linac |
| url | https://nasplib.isofts.kiev.ua/handle/123456789/81377 |
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