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High-power ion beam sources for industrial application
Surfaceand Coatings Technology96 (1997) 103-109
High-power ion beam sources for industrial application G.E. Remnev as*, I.F. Isakov a, M.S. Opekounov a, G.I. Kotlyarevsky a, V.L. K&uzov b, VS. Lopatin a, V.M. Matvienko a, M-.Yu. Ovsyagnikov b, A.V. Potyomkin a, V.A. Tarbokov a ’ Nuclcas Physics Institute, Lenin Street 2A, 634050 Tomsk, Russia b Lifzetron Scient$c Industrial Etzterprise, Layin Street 11, 603107 hC Nol;gorod, Russia
Received21 June 1996;accepted25 February 1997
Abstract Two sourcesof high-powerion beamsof nanosecondduration are described,a MUK and a TEMP unit. They generatedions with energiesof up to 150 and 300keV, respectively,and the pulseduration was20-200 and 50 ns, respectively.For the MUK unit, beamparametersfor heavy ion implantation (Al”+, Mgnt, Fe”*, Wni, etc.) were as follows: current density ranging from 1 to 10Acr1~-~ and total ion flux energy up to 20J. For the TEMP unit, the following beamparameterswere usedfor H+ and C”’ ions: current density40-200 A cmw2and total ion flux energy0.3-0.5 kJ. The sourcesare poweredby various diode systems and can be applied in material sciencefor scientificresearchand technology. 0 1997ElsevierScienceS.A. Keyir’ords:
High-power ion beams;Surfacemodification; Short pulseion implantation
1. MUK supercurrent short-pulse implanter Applied research pertaining to the modification of material properties is mainly carried out by two methods: (1) implantation treatment of materials and (2) investigation of the effect of exposure of materials to a concentrated energy flux (high-power ion beam) [ 1,2]. For implantation treatment, the properties of modified materials are largely defined by the type and dose (D) of implanted ions; for semiconductors and metals, the D values are 10’4-10’” and 10’6-1019 cmm2, respectively. When material is subjected to treatment by a high-power ion beam (HPIB), the resulting changes in its properties depend mainly on the beam power density, with the type of ions implanted also being of importance. Experimentally, it has been found that if implantation treatment heats the metal undersurface layer to temperatures approximately equal to or exceeding the melting point of the material being treated, the structure of the surface layers is restored during the course of treatment [ 11. Short-pulse ion implantation is advantageous because it allows one to combine in one operation the implantation of doping additions and annealing of defects emerging in the surface layer structure due to the action of HPIB. The following requirements are imposed on such short-pulse high-current implanter machines: high pulse repetition frequency, long lifetime, a possibility of * Corresponding author. 0257-8972/97/$17.00 Q 1997Elsevier Science S.A. All rightsreserved. PIZ SO257-8972(97)00116-3
varying the type of ions and power flux density. The short-pulse ion beams accelerator for ion implantation (MUK source) developed at the Nuclear Physics Institute (Tomsk, Russia) meets the above requirements. 1.1. Basic components
of the MUK source
The machine comprises an initial energy-storing unit, a step-up peaking transformer, a nanosecond pulse generator, a step-down current generator for setting up pulsed magnetic fields and a vacuum chamber equipped with an ion diode (Fig. 1). Diodes of two types, i.e. a planar diode and a magnetically insulated strip diode (MID), were used. The nanosecond pulse generator consists of a single forming line and two transmission lines using a cable with 24 R wave resistance. It allows the formation of a single pulse or a series of voltage pulses of arbitrary polarity [3], and makes it possible to vary the pulse timing by changing the length of the transmission lines. The amplitude of the voltage pulse at the ion diode is up to 150 kV, and the pulse duration and pulse interval are determined by the length of both the forming and the delay lines. The- use ofa transfer lineallows th-e ion-generating unit of the machine and the vacuum chamber, where implantation proper is carried out, to be placed in different rooms. The Marx generator used in &previous study on short-pulse implantation for charging the pulse-forming line [3,4] was replaced by a step-up
G.E. Remnev
er d. J Sqfuce
rind Coutings
Fig. 1. Basic components of the MUK short-pulse implanter. (1) Initial energy storing unit of nanosecond pulse voltage generator: C,, capacity of a primary accumulator of nanosecond pulse voltage generator; Trr,, step-up peaking transformer; U, switch IRT-6; Dr, S, switch starting unit. (2) Nanosecond pulse voltage generator: FL, single forming line; TL,, TL,, transmission lines; Si, Sz, S,, gas switches. (3) Initial energy storing unit of pulse magnetic field generator: Cti capacity of primary accumulator of pulse magnetic field generator. (4) Vacuum chamber with MID. (5) Vacuum pump. (6) Synchronization unit.
peaking transformer with an output voltage of 300 kV and transfer coefficient of 24. The step-up peaking transformer and the starting unit of the gas switches of the nanosecond pulse generator are placed in an oil vessel. The scheme of the starting unit of switches is described in Ref. [S]. It should be noted here that the scheme permits the energy to be transfered completely from the initial energy storing unit to the forming line and automatically starts the gas switches at peak charge voltage in the forming line. The voltage pulse repetition rate is from single pulse up to 10 Hz. To set up a pulsed insulation magnetic field in the ion diode, the current source circuit of a generator with a step-down peak transformer having a transfer coefficient of l/10 is used. This transformer is placed on the vacuum chamber near the strip coil cathode, thus reducing current loss and increasing the energy transfer efficiency of the circuit to 86%. The amplitude of the insulation current is up to 60 kA and the current pulse duration 20 ps. 1.2. MUK source diode systemsand ion beamparameters
In order to realize the multipurpose goals of implantation and HPIB treatment, operations with several types of diodes are provided in our short-pulse implanter. A planar diode can be used to obtain beams of small crosssection with ion current densities less than 1 A cm-‘, where the material of the anode determines the dopant. The nanosecond generator of a MUK unit is capable of operating in a bipolar pulse mode, where the first negative voltage pulse is intended to form the plasma on the surface of the potential electrode, and the second positive
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pulse is intended to accelerate ions out of the formed plasma 161. This allows the ion flux of any composition to be obtained from an explosion-emission plasma, since explosion-emission may occur on the surface of any material. Therefore the composition of the explosionemission plasma depends solely on the potential electrode material and the state of its surface 171. The MID with crossed magnetic field (Fig. 2) is used to obtain beams of large cross-section (up to 45 x 200 mm’). In this diode type, the magnetic field is set up by the coil cathode current supplied from an external power source. The cathode unit design of MID provides the magnetic insulation of the electron flux in the whole anode-cathode gap and controls the electron flux on to the anode surface, It allows the efficiency of plasma formation on the anode surface to be controlled and emission homogeneity to be attained. The MID anode is made from aluminum; however, the coating of its active part can be replaced by insertions of another type of material. Its dimensions are as follows: width 45 mm, length 200 mm, area of active part 80 cm’. The cathode encloses the anode. The cathode strip is the load for the current transformer of the system for setting up a magnetic field. The cathode strip is 45 mm wide and 4 mm t’hick. On the beam output side of the cathode there is a system of slits, each measuring 4 x 40 mm, with the total cathode transparency being equal to 60%. The MUK implanter operation in a unipolar pulse mode of a nanosecond generator was carried out using a polyethylene-coated anode. The anode coating had a set of holes 0.5 mm in diameter with a spacing of 4 mm. The output ion flux had the following dimensions: 45 x200 mm’ in the case of a parallel electrode or 50 x 50 mm’ in the case of a ballistic focusing diode. The beam components were mainly carbon ions and protons. Ion current densities from 4 to 20 A cm-’ in impulse were obtained. The total current was reached 4 kA. To generate heavy ion beams, the MUK implanter operation was performed in bipolar pulse mode of the nanosecond generator using MID. The anode insert of the MID potential electrode was made from the same material that was necessary for implantation. In twopulse operational mode of a nanosecond generator the plasma is formed on applying the first negative pulse of voltage on a potential electrode; the structure of the plasma is determined by the material of the anode insert. The acceleration of ions takes place on applying the second positive impulse of voltage from the nanosecond generator from the formed boundary of plasma. Let us consider the case of MID with a potential electrode insert made from Al. The output ion flux had the following dimensions: 45 x 200 mm2 or 90 x 200 mm2. Ion current densities from 4 to 10 A cm-’ in impulse were obtained. The total current of the output beam was up to 1.5 kA. Oscillograms of the accelerating voltage pulses and ion current density are shown in
from
nanosecond
generator
Fig. 2. Vacuum chamber with MID of the MUK implanter.
Fig. 3. A typical Thomson plate image of ion beam components and their spectra is presented in Figs. 4 and 5. When Al”’ ions are generated, they make up 70% of the composition of the beam, the remaining 30% being represented by Hi and C”’ ions. Energetic and mass characteristics of the accelerated ion beam were determinated using a Thomson spectrometer. A CR-39 plate detector (MOM-Atomki Nuclear Track Detector, type MA-ND/p) was used as a detector [8]. The diode voltage and total current were measured using an active voltage divider and a Rogowsky coil. The ion current density was registered using a collimated Faraday cup. Ud,kV
Id,kA.
120
-
-
5.2
90
-
-
3.9
60
-
-
2.6
30
-
2. TEMP sourceof HPIBs
HPIB surface modification treatment has advantages over similar techniques introduced on an industrial scale, cg?oti-itiplantation and application of wear-resistant coatings, because of a reduction in specific energy consumption and an increase in productivity. On metal treatment by HPIB action of nanosecond duration, these undergo structural changes (mainly in the near-surface layers) and carbides of target components are formed. The carbon is diffused in and then absorbed on the metal surface taking part in the reaction [2,9]. The functional capabilities of a practical application of HPIB are extended because of the possibility of surface deposition of films with specific chemical composition prior to exposure of the same surface to HPIB, thereby providing mixing of layers in the course of HPIB treatment. HPIB treatment also allows metastable compounds to be obtained that are practically inaccessible by other techniques. A similar approach is used in the laser implantation technique [lo]. 2.1. Basic componentsof the TEMP source
0
160
320
480
640
7, ns
Fig. 3. Diode voltage U, (solid line), diode total current I, (dotted) and ion current density J, at the target. Bipolar mode of nanosecond pulse voltage generator. MID with aluminum anode insertion with
protrusions on its active part.
A general view of the TEMP accelerator and its vacuum chamber is displayed in Fig. 6. The unit includes also a semi-automatic remote control panel and a carousel specimen-handling system installed in the vacuum chamber. Specimen treatment can be performed in both manual and automatic control modes. The time required for opening the chamber, replacing the changeable carousel unit with specimens, chamber pressurization and pumping to an operation pressure of lo-’ Pa is 10 min. A Marx generator includes seven stages
106
Fig. 4. Typical Thomson piate image, MID with aluminum anode insertion.
incorporating capacitors charged from a high-voltage source to 40-50 kV, inductors serving as charging resistors for the capacitors and a gas-tiled tube with discharge gaps. The discharge gaps of the Marx generator are discharges in which the principle of electric field distortion is applied. A modified pulse-forming line (PFL) unit with deionized water serving as dielectric comprises compressed-gas switches ( 1,4) with self-healing breakdown and a charging inductor (3) installed in front of the gun. Pulse voltage parameters are controlled by means of the interelectrode gap spacing and by the gas pressure in the PFL switches. The accelerator has autonomous water preparation, an autonomous oil system and a vacuum system comprising a diffusion pump. The vacuum chamber is a 500 mm section of a stainless-steel tube 500 mm in diameter. On its lateral portion there are three windows and several high-voltage power and signal bushings for physical and optical diagnostics. Beams are produced by the MIDs without external magnetic field ( 12). To provide mixing of the target multilayer, a device intended for thin metal film deposition on treated surfaces is installed in the vacuum chamber. It allows the magnetron technique to be used for target sputtering and films of various materials to be obtained. Two magnetron film depositors (16) with dimensions of 300 x 100 x 30 mm3 are installed at the back flange inside the vacuum chamber opposite MID. The magnetrons supplied by the power supply system comprise two 3 kW N
c
sources each with a voltage up to 1 kV as well as gasfeeding and water-cooling systems. HPIB treatment and film deposition can be performed in any desired sequence without causing any depressurization of the vacuum space. The time of film deposition depends on both the film thickness and the materi,: sputtered. The current density at the target is controlled by the gap between the target unit and the focusing diode. Thus, the functional capabilities of the machine have been extended, which enables it to perform the following operations in a single cycle: (I ) deposition and mixing of the metal film with the substrate by HP13 treatment; (2) target pretreatment and metal film deposition; (3) target pretreatment, film deposition and mixing of the materials by HPIB treatment; (4) target pretreatment, deposition of two metal films in succession in a single cycle or in N cycles and mixing of the metal films by HPIB treatment. The installation is amenable to improvement and can be adapted to other operations.
Al’
C’
-L-l
I
AI*
Al”’
/; , :*I i 4
8
12
16
20
24
28
A/Z
Fig. 5. Mass spectrum of ion beam. MID with aluminum anode insertion.
Fig. 6. Schematic diagram of the TEMP accelerator. 1,4, Switches; 2, modified pulse forming line electrodes; 3, charging inductor; 5, voltage dividers; 7,9,10, Rogowsky coil; 11, vacuum chamber; 11, MID; 13, target unit; 14, vacuum pump Facilities; 15, Marx generator; 16, magnetron Urn depositors.
G.E. Rrr~no~
er nl. / Surface
and Coatings
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96 (1997) from
103-109
107
nanosecond
Fig. 7. Vacuum chamber of the TEMP accelerator with MID and carousel for targets.
To produce pulsed ion beams with energy of 300 keV and current density up to 200 A cmv2, MID is used in the TEMP unit under a magnetic self-insulation mode Fig. 7. The major advantages of this type of diode over other diode systems are its long service life and the stability of the ion beam parameters [ 1 I]. The ground electrode of MID has the shape of an open coil, one end of which is connected to the vacuum chamber. The electrodes are 40 mm wide and their working portion is 200 mm long. The potential electrode is made from graphite. The nanosecond pulser of the accelerator forms two high-voltage pulses of opposite polarities with amplitudes of 150 kV and 300 kV, with the first one of negative polarity serving for plasma generation and the second one of positive polarity for ion acceleration. Fig. 8 presents oscillograms of diode voltage and ion current density. The beam composition depends mainly on the material of the potential electrode and on the state of the graphite surface. As can be seen from Fig. 9,
the time-of-flight procedure and diagnostics on a Thomson spectrometer indicate that the beam generated is composed of carbon ions and protons (70 and 30%. respectively). The distribution of HPIB power densities at the target measured by means of a sectioned calorimeter is illustrated in Fig. 10. To obtain more uniform distribution of HIPIB power densities at the target, additional measurements on beam generation and transportation are required.
3. Conclusion A new version of ion beam treatment of materials has been elaborated. The possibility is offered of varying the portion of energy action due to the capability of the
-J ‘{, Wcm2
U, MeV
033
092
0,15
O,l
-250 -500 0
a!
. /
t:, ns
Fig. 8. Oscillograms of the voltage and ion current density at the target.
Fig. 9. Thomson spectrogram of the composition of an ion beam from the TEMP accelerator.
108
G.E. Rernnev
er al. / Sqfuce
and Coarings
Technolog~~ 96 (1997)
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0.0
’
60
Fig. 10. Distribution of power density HPIB received by focusing diode system on the target measured by mems of a sectioned calorimeter.
source to control the current density and exposure time, as well as using different kinds of ions. It raises new possibilities for surface modification of a wide range of materials, e.g. dielectrics, semiconductors and metals. The MUK and TEMP accelerators have different applications. The first accelerator is used for ion implantation and the second one for intense ion energy effects. The accelerators are based on the same approach of ion formation in diode systems. In trials, the MUK implanter has been found to be accurate for over 107 operations, with no significant impairment in its performance being observed. The ion beams Al”+, C”+ and H+, with energy 30-150 keV n-‘, ion charge II= 1-3, ion current densities from 4 to 20 A cm-* per pulse? are obtained. For a current pulse repetition from single pulse up to 10 Hz the rate of dose accumulation for characteristic ions was up to 10’4cm-2 s-l for H’ and C+ ions and up to 1Or3 crnv2 s-l for Al”+ ions. The TEMP accelerator generates beams with optimal parameters for most operations involving surface modification of cutting tools and other items. TEMP source has been developed for industrial application using the results of investigations of the effect of exposure to HPIBs of various materials that were obtained on installations of different types [ 12,131. The treatment of
steel tools irradiated by HPIB with more than 100 A cm-~2 current density, with more than two pulses, leads to the formation of line-grained structures in the near-surface layer. Polished specimens, which are subjected to the HPIB treatment, have a high level of surface roughness compared to the original ones, while a similar treatment of specimens with rougher surfaces leads to the smoothing of the surface and an improvement in the surface characteristics. As a result of HPIB treatment, the density of dislocations in the near-surface layer and depth of ion rate in the specimen have been found to increase by one or two orders of magnitude, with a resultant three-fold or better increase in the wear resistance of the treated surface. The SIE Linetron and the Temp Engineering Physical Center of Nuclear Physics Institute have developed the industrial technology for hardening cutting tools on the basis of the TEMP accelerator for the treatment of wagon wheels. Annual produ.ction has reached 100 000 plates per year. The accelerator resource is more than lo6 times at present. Dependmg on the sort of tools and state of the treated surfaces the tool hardening is increased by as much as two to six-fold. A photograph of the vacuum chamber of the industrial facility for cutting tool treatment is presented in Fig. 11. The industrial application of the TEMP accelerator
Fig. Il. Photograph of the vacuum chamber of an industrial facility for cutting tool treatment. Table 1 The accelerator parameters
Accelerated ion energy (keV) Density of an ion current (A cm-‘) Duration of a pulse of a current (ns) Frequency of recurrence of pulses of a current (s-i) Speed of processing (cm2 h-i) Volume of a load of the tool in one operation cycle Complete time of processing (h)
TEMP- 1
TEMP-l
300 50-200 50 0.25
300 50-200 50 1
lo4 100
4, lOA 400
1
1
for tool hardening promises wide perspectives for the use of the high-power ion beam source in industry. The next TEMP-4 accelerator with increased productivity and 1 Hz repetition rate will be put into the operation in the near future. Table 1 shows the parameters of the new TEMP-4 accelerator compared to the parameters of the operating TEMP-1 accelerator, as well as the parameters of technological processes of treatment for these accelerators.
References [ 11 F.F. Komarov, A.P. Novikov, New methods of ion-beam treatment of semiconductor crystals. Itogi Nauki i Tekhniki. Ser. Fiz-
icheskiye Osnovy Lazernoi i Puchkovoi Tekhnologii, vol. 5-M, ~~~~Viniti, 1989, p. 135 (in Russian). -~[2] G.E. Remnev, V.A. Shulov, Laser Particle Beams 14 (1993) 707-731. -[3] I.F. Isakov, V.N. Kolodii. MIS. Opekounov. V.M. Matvienko, S.A. Pechenkin, GE. Remnev. Yu.P. Usov, Vacuum 42 (1991) 159-162. [4] A.D. Pogrebnjak, I.F. Isakov, MS. Opekounov. Sh.M. Ruzimov. A.E. Ligachev, A.V. Nesmelov, I.B. Kurakin, Phps. Lett. A 123 (8) (1987) 410-412. l51 V.V. Vasilvev. E.I. Luconin. E.G. Furman. Priborv i Tekhnika Eksperimenta. no. 6, 1988, pp. 99-102 (in Russian). [6] I.F. Isakov. E.I. Logathev, MS. Opekounov. S.A. Pechenkin. G.E. Remnev, Yu,P. Usov, Pribory i Tekhnika Eksperimenta, no. -3~987,1101--1T)3(InR~~~~~~~~~ ~~ ~ [7] E.I. Logathev, G.E. Remnev, Yu.P. Usov, Pisma v J Techn. Phys. 6 (1980) 1304-1406 (in Russian). [8] G.E. Remnev. M.S. Opekounov, A.N. Grishin. I.V. Ivonin, Radiat. Measurements 25 (l-4) (1995) 739-730. [9] A.D. Pogrebnyak. G.E. Remnev, S.A. Chistyakov, A.E. Ligachev, Izvestiya VUZ’ov, Fizika 1 (1987) 52-65 (in Russian). [IO] Yu.R. Bykovsky, V.N. Nevolin, V.Yu. Fominskii, Ion and Laser Implantation of Metal Materials. Energoatomizdat, Moscow, 1991, p, 240. [ 1l] V.M. Bystritskii, A.N. Didenko, High-intensity Ion Beams, Energoatomizdat, Moscow. 1984, p. 52 (in Russian). [12] E.I. Logathev, G.E. Remnev, Yu.P. Usov, P&ory i Tekhnika Eksperimenta. no. 1. 1983. pp. 21-23 (in Russian). [13] D.R. Akerman. I.F. Isakov. V.N. Kolodii. MSOpekounov, G.E. Remnev, “TEMP” high power ion beams accelerator (Abstract). 1st All-Union Conference, Modification of the Properties of Design Materials by Charged Particle Beams, Tomsk, 1988, Part 1. pp. 34.
High-power ion beam sources for industrial application G.E. Remnev as*, I.F. Isakov a, M.S. Opekounov a, G.I. Kotlyarevsky a, V.L. K&uzov b, VS. Lopatin a, V.M. Matvienko a, M-.Yu. Ovsyagnikov b, A.V. Potyomkin a, V.A. Tarbokov a ’ Nuclcas Physics Institute, Lenin Street 2A, 634050 Tomsk, Russia b Lifzetron Scient$c Industrial Etzterprise, Layin Street 11, 603107 hC Nol;gorod, Russia
Received21 June 1996;accepted25 February 1997
Abstract Two sourcesof high-powerion beamsof nanosecondduration are described,a MUK and a TEMP unit. They generatedions with energiesof up to 150 and 300keV, respectively,and the pulseduration was20-200 and 50 ns, respectively.For the MUK unit, beamparametersfor heavy ion implantation (Al”+, Mgnt, Fe”*, Wni, etc.) were as follows: current density ranging from 1 to 10Acr1~-~ and total ion flux energy up to 20J. For the TEMP unit, the following beamparameterswere usedfor H+ and C”’ ions: current density40-200 A cmw2and total ion flux energy0.3-0.5 kJ. The sourcesare poweredby various diode systems and can be applied in material sciencefor scientificresearchand technology. 0 1997ElsevierScienceS.A. Keyir’ords:
High-power ion beams;Surfacemodification; Short pulseion implantation
1. MUK supercurrent short-pulse implanter Applied research pertaining to the modification of material properties is mainly carried out by two methods: (1) implantation treatment of materials and (2) investigation of the effect of exposure of materials to a concentrated energy flux (high-power ion beam) [ 1,2]. For implantation treatment, the properties of modified materials are largely defined by the type and dose (D) of implanted ions; for semiconductors and metals, the D values are 10’4-10’” and 10’6-1019 cmm2, respectively. When material is subjected to treatment by a high-power ion beam (HPIB), the resulting changes in its properties depend mainly on the beam power density, with the type of ions implanted also being of importance. Experimentally, it has been found that if implantation treatment heats the metal undersurface layer to temperatures approximately equal to or exceeding the melting point of the material being treated, the structure of the surface layers is restored during the course of treatment [ 11. Short-pulse ion implantation is advantageous because it allows one to combine in one operation the implantation of doping additions and annealing of defects emerging in the surface layer structure due to the action of HPIB. The following requirements are imposed on such short-pulse high-current implanter machines: high pulse repetition frequency, long lifetime, a possibility of * Corresponding author. 0257-8972/97/$17.00 Q 1997Elsevier Science S.A. All rightsreserved. PIZ SO257-8972(97)00116-3
varying the type of ions and power flux density. The short-pulse ion beams accelerator for ion implantation (MUK source) developed at the Nuclear Physics Institute (Tomsk, Russia) meets the above requirements. 1.1. Basic components
of the MUK source
The machine comprises an initial energy-storing unit, a step-up peaking transformer, a nanosecond pulse generator, a step-down current generator for setting up pulsed magnetic fields and a vacuum chamber equipped with an ion diode (Fig. 1). Diodes of two types, i.e. a planar diode and a magnetically insulated strip diode (MID), were used. The nanosecond pulse generator consists of a single forming line and two transmission lines using a cable with 24 R wave resistance. It allows the formation of a single pulse or a series of voltage pulses of arbitrary polarity [3], and makes it possible to vary the pulse timing by changing the length of the transmission lines. The amplitude of the voltage pulse at the ion diode is up to 150 kV, and the pulse duration and pulse interval are determined by the length of both the forming and the delay lines. The- use ofa transfer lineallows th-e ion-generating unit of the machine and the vacuum chamber, where implantation proper is carried out, to be placed in different rooms. The Marx generator used in &previous study on short-pulse implantation for charging the pulse-forming line [3,4] was replaced by a step-up
G.E. Remnev
er d. J Sqfuce
rind Coutings
Fig. 1. Basic components of the MUK short-pulse implanter. (1) Initial energy storing unit of nanosecond pulse voltage generator: C,, capacity of a primary accumulator of nanosecond pulse voltage generator; Trr,, step-up peaking transformer; U, switch IRT-6; Dr, S, switch starting unit. (2) Nanosecond pulse voltage generator: FL, single forming line; TL,, TL,, transmission lines; Si, Sz, S,, gas switches. (3) Initial energy storing unit of pulse magnetic field generator: Cti capacity of primary accumulator of pulse magnetic field generator. (4) Vacuum chamber with MID. (5) Vacuum pump. (6) Synchronization unit.
peaking transformer with an output voltage of 300 kV and transfer coefficient of 24. The step-up peaking transformer and the starting unit of the gas switches of the nanosecond pulse generator are placed in an oil vessel. The scheme of the starting unit of switches is described in Ref. [S]. It should be noted here that the scheme permits the energy to be transfered completely from the initial energy storing unit to the forming line and automatically starts the gas switches at peak charge voltage in the forming line. The voltage pulse repetition rate is from single pulse up to 10 Hz. To set up a pulsed insulation magnetic field in the ion diode, the current source circuit of a generator with a step-down peak transformer having a transfer coefficient of l/10 is used. This transformer is placed on the vacuum chamber near the strip coil cathode, thus reducing current loss and increasing the energy transfer efficiency of the circuit to 86%. The amplitude of the insulation current is up to 60 kA and the current pulse duration 20 ps. 1.2. MUK source diode systemsand ion beamparameters
In order to realize the multipurpose goals of implantation and HPIB treatment, operations with several types of diodes are provided in our short-pulse implanter. A planar diode can be used to obtain beams of small crosssection with ion current densities less than 1 A cm-‘, where the material of the anode determines the dopant. The nanosecond generator of a MUK unit is capable of operating in a bipolar pulse mode, where the first negative voltage pulse is intended to form the plasma on the surface of the potential electrode, and the second positive
Teel~nology
96 (1997)
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pulse is intended to accelerate ions out of the formed plasma 161. This allows the ion flux of any composition to be obtained from an explosion-emission plasma, since explosion-emission may occur on the surface of any material. Therefore the composition of the explosionemission plasma depends solely on the potential electrode material and the state of its surface 171. The MID with crossed magnetic field (Fig. 2) is used to obtain beams of large cross-section (up to 45 x 200 mm’). In this diode type, the magnetic field is set up by the coil cathode current supplied from an external power source. The cathode unit design of MID provides the magnetic insulation of the electron flux in the whole anode-cathode gap and controls the electron flux on to the anode surface, It allows the efficiency of plasma formation on the anode surface to be controlled and emission homogeneity to be attained. The MID anode is made from aluminum; however, the coating of its active part can be replaced by insertions of another type of material. Its dimensions are as follows: width 45 mm, length 200 mm, area of active part 80 cm’. The cathode encloses the anode. The cathode strip is the load for the current transformer of the system for setting up a magnetic field. The cathode strip is 45 mm wide and 4 mm t’hick. On the beam output side of the cathode there is a system of slits, each measuring 4 x 40 mm, with the total cathode transparency being equal to 60%. The MUK implanter operation in a unipolar pulse mode of a nanosecond generator was carried out using a polyethylene-coated anode. The anode coating had a set of holes 0.5 mm in diameter with a spacing of 4 mm. The output ion flux had the following dimensions: 45 x200 mm’ in the case of a parallel electrode or 50 x 50 mm’ in the case of a ballistic focusing diode. The beam components were mainly carbon ions and protons. Ion current densities from 4 to 20 A cm-’ in impulse were obtained. The total current was reached 4 kA. To generate heavy ion beams, the MUK implanter operation was performed in bipolar pulse mode of the nanosecond generator using MID. The anode insert of the MID potential electrode was made from the same material that was necessary for implantation. In twopulse operational mode of a nanosecond generator the plasma is formed on applying the first negative pulse of voltage on a potential electrode; the structure of the plasma is determined by the material of the anode insert. The acceleration of ions takes place on applying the second positive impulse of voltage from the nanosecond generator from the formed boundary of plasma. Let us consider the case of MID with a potential electrode insert made from Al. The output ion flux had the following dimensions: 45 x 200 mm2 or 90 x 200 mm2. Ion current densities from 4 to 10 A cm-’ in impulse were obtained. The total current of the output beam was up to 1.5 kA. Oscillograms of the accelerating voltage pulses and ion current density are shown in
from
nanosecond
generator
Fig. 2. Vacuum chamber with MID of the MUK implanter.
Fig. 3. A typical Thomson plate image of ion beam components and their spectra is presented in Figs. 4 and 5. When Al”’ ions are generated, they make up 70% of the composition of the beam, the remaining 30% being represented by Hi and C”’ ions. Energetic and mass characteristics of the accelerated ion beam were determinated using a Thomson spectrometer. A CR-39 plate detector (MOM-Atomki Nuclear Track Detector, type MA-ND/p) was used as a detector [8]. The diode voltage and total current were measured using an active voltage divider and a Rogowsky coil. The ion current density was registered using a collimated Faraday cup. Ud,kV
Id,kA.
120
-
-
5.2
90
-
-
3.9
60
-
-
2.6
30
-
2. TEMP sourceof HPIBs
HPIB surface modification treatment has advantages over similar techniques introduced on an industrial scale, cg?oti-itiplantation and application of wear-resistant coatings, because of a reduction in specific energy consumption and an increase in productivity. On metal treatment by HPIB action of nanosecond duration, these undergo structural changes (mainly in the near-surface layers) and carbides of target components are formed. The carbon is diffused in and then absorbed on the metal surface taking part in the reaction [2,9]. The functional capabilities of a practical application of HPIB are extended because of the possibility of surface deposition of films with specific chemical composition prior to exposure of the same surface to HPIB, thereby providing mixing of layers in the course of HPIB treatment. HPIB treatment also allows metastable compounds to be obtained that are practically inaccessible by other techniques. A similar approach is used in the laser implantation technique [lo]. 2.1. Basic componentsof the TEMP source
0
160
320
480
640
7, ns
Fig. 3. Diode voltage U, (solid line), diode total current I, (dotted) and ion current density J, at the target. Bipolar mode of nanosecond pulse voltage generator. MID with aluminum anode insertion with
protrusions on its active part.
A general view of the TEMP accelerator and its vacuum chamber is displayed in Fig. 6. The unit includes also a semi-automatic remote control panel and a carousel specimen-handling system installed in the vacuum chamber. Specimen treatment can be performed in both manual and automatic control modes. The time required for opening the chamber, replacing the changeable carousel unit with specimens, chamber pressurization and pumping to an operation pressure of lo-’ Pa is 10 min. A Marx generator includes seven stages
106
Fig. 4. Typical Thomson piate image, MID with aluminum anode insertion.
incorporating capacitors charged from a high-voltage source to 40-50 kV, inductors serving as charging resistors for the capacitors and a gas-tiled tube with discharge gaps. The discharge gaps of the Marx generator are discharges in which the principle of electric field distortion is applied. A modified pulse-forming line (PFL) unit with deionized water serving as dielectric comprises compressed-gas switches ( 1,4) with self-healing breakdown and a charging inductor (3) installed in front of the gun. Pulse voltage parameters are controlled by means of the interelectrode gap spacing and by the gas pressure in the PFL switches. The accelerator has autonomous water preparation, an autonomous oil system and a vacuum system comprising a diffusion pump. The vacuum chamber is a 500 mm section of a stainless-steel tube 500 mm in diameter. On its lateral portion there are three windows and several high-voltage power and signal bushings for physical and optical diagnostics. Beams are produced by the MIDs without external magnetic field ( 12). To provide mixing of the target multilayer, a device intended for thin metal film deposition on treated surfaces is installed in the vacuum chamber. It allows the magnetron technique to be used for target sputtering and films of various materials to be obtained. Two magnetron film depositors (16) with dimensions of 300 x 100 x 30 mm3 are installed at the back flange inside the vacuum chamber opposite MID. The magnetrons supplied by the power supply system comprise two 3 kW N
c
sources each with a voltage up to 1 kV as well as gasfeeding and water-cooling systems. HPIB treatment and film deposition can be performed in any desired sequence without causing any depressurization of the vacuum space. The time of film deposition depends on both the film thickness and the materi,: sputtered. The current density at the target is controlled by the gap between the target unit and the focusing diode. Thus, the functional capabilities of the machine have been extended, which enables it to perform the following operations in a single cycle: (I ) deposition and mixing of the metal film with the substrate by HP13 treatment; (2) target pretreatment and metal film deposition; (3) target pretreatment, film deposition and mixing of the materials by HPIB treatment; (4) target pretreatment, deposition of two metal films in succession in a single cycle or in N cycles and mixing of the metal films by HPIB treatment. The installation is amenable to improvement and can be adapted to other operations.
Al’
C’
-L-l
I
AI*
Al”’
/; , :*I i 4
8
12
16
20
24
28
A/Z
Fig. 5. Mass spectrum of ion beam. MID with aluminum anode insertion.
Fig. 6. Schematic diagram of the TEMP accelerator. 1,4, Switches; 2, modified pulse forming line electrodes; 3, charging inductor; 5, voltage dividers; 7,9,10, Rogowsky coil; 11, vacuum chamber; 11, MID; 13, target unit; 14, vacuum pump Facilities; 15, Marx generator; 16, magnetron Urn depositors.
G.E. Rrr~no~
er nl. / Surface
and Coatings
Teholog~,
96 (1997) from
103-109
107
nanosecond
Fig. 7. Vacuum chamber of the TEMP accelerator with MID and carousel for targets.
To produce pulsed ion beams with energy of 300 keV and current density up to 200 A cmv2, MID is used in the TEMP unit under a magnetic self-insulation mode Fig. 7. The major advantages of this type of diode over other diode systems are its long service life and the stability of the ion beam parameters [ 1 I]. The ground electrode of MID has the shape of an open coil, one end of which is connected to the vacuum chamber. The electrodes are 40 mm wide and their working portion is 200 mm long. The potential electrode is made from graphite. The nanosecond pulser of the accelerator forms two high-voltage pulses of opposite polarities with amplitudes of 150 kV and 300 kV, with the first one of negative polarity serving for plasma generation and the second one of positive polarity for ion acceleration. Fig. 8 presents oscillograms of diode voltage and ion current density. The beam composition depends mainly on the material of the potential electrode and on the state of the graphite surface. As can be seen from Fig. 9,
the time-of-flight procedure and diagnostics on a Thomson spectrometer indicate that the beam generated is composed of carbon ions and protons (70 and 30%. respectively). The distribution of HPIB power densities at the target measured by means of a sectioned calorimeter is illustrated in Fig. 10. To obtain more uniform distribution of HIPIB power densities at the target, additional measurements on beam generation and transportation are required.
3. Conclusion A new version of ion beam treatment of materials has been elaborated. The possibility is offered of varying the portion of energy action due to the capability of the
-J ‘{, Wcm2
U, MeV
033
092
0,15
O,l
-250 -500 0
a!
. /
t:, ns
Fig. 8. Oscillograms of the voltage and ion current density at the target.
Fig. 9. Thomson spectrogram of the composition of an ion beam from the TEMP accelerator.
108
G.E. Rernnev
er al. / Sqfuce
and Coarings
Technolog~~ 96 (1997)
103-109
0.0
’
60
Fig. 10. Distribution of power density HPIB received by focusing diode system on the target measured by mems of a sectioned calorimeter.
source to control the current density and exposure time, as well as using different kinds of ions. It raises new possibilities for surface modification of a wide range of materials, e.g. dielectrics, semiconductors and metals. The MUK and TEMP accelerators have different applications. The first accelerator is used for ion implantation and the second one for intense ion energy effects. The accelerators are based on the same approach of ion formation in diode systems. In trials, the MUK implanter has been found to be accurate for over 107 operations, with no significant impairment in its performance being observed. The ion beams Al”+, C”+ and H+, with energy 30-150 keV n-‘, ion charge II= 1-3, ion current densities from 4 to 20 A cm-* per pulse? are obtained. For a current pulse repetition from single pulse up to 10 Hz the rate of dose accumulation for characteristic ions was up to 10’4cm-2 s-l for H’ and C+ ions and up to 1Or3 crnv2 s-l for Al”+ ions. The TEMP accelerator generates beams with optimal parameters for most operations involving surface modification of cutting tools and other items. TEMP source has been developed for industrial application using the results of investigations of the effect of exposure to HPIBs of various materials that were obtained on installations of different types [ 12,131. The treatment of
steel tools irradiated by HPIB with more than 100 A cm-~2 current density, with more than two pulses, leads to the formation of line-grained structures in the near-surface layer. Polished specimens, which are subjected to the HPIB treatment, have a high level of surface roughness compared to the original ones, while a similar treatment of specimens with rougher surfaces leads to the smoothing of the surface and an improvement in the surface characteristics. As a result of HPIB treatment, the density of dislocations in the near-surface layer and depth of ion rate in the specimen have been found to increase by one or two orders of magnitude, with a resultant three-fold or better increase in the wear resistance of the treated surface. The SIE Linetron and the Temp Engineering Physical Center of Nuclear Physics Institute have developed the industrial technology for hardening cutting tools on the basis of the TEMP accelerator for the treatment of wagon wheels. Annual produ.ction has reached 100 000 plates per year. The accelerator resource is more than lo6 times at present. Dependmg on the sort of tools and state of the treated surfaces the tool hardening is increased by as much as two to six-fold. A photograph of the vacuum chamber of the industrial facility for cutting tool treatment is presented in Fig. 11. The industrial application of the TEMP accelerator
Fig. Il. Photograph of the vacuum chamber of an industrial facility for cutting tool treatment. Table 1 The accelerator parameters
Accelerated ion energy (keV) Density of an ion current (A cm-‘) Duration of a pulse of a current (ns) Frequency of recurrence of pulses of a current (s-i) Speed of processing (cm2 h-i) Volume of a load of the tool in one operation cycle Complete time of processing (h)
TEMP- 1
TEMP-l
300 50-200 50 0.25
300 50-200 50 1
lo4 100
4, lOA 400
1
1
for tool hardening promises wide perspectives for the use of the high-power ion beam source in industry. The next TEMP-4 accelerator with increased productivity and 1 Hz repetition rate will be put into the operation in the near future. Table 1 shows the parameters of the new TEMP-4 accelerator compared to the parameters of the operating TEMP-1 accelerator, as well as the parameters of technological processes of treatment for these accelerators.
References [ 11 F.F. Komarov, A.P. Novikov, New methods of ion-beam treatment of semiconductor crystals. Itogi Nauki i Tekhniki. Ser. Fiz-
icheskiye Osnovy Lazernoi i Puchkovoi Tekhnologii, vol. 5-M, ~~~~Viniti, 1989, p. 135 (in Russian). -~[2] G.E. Remnev, V.A. Shulov, Laser Particle Beams 14 (1993) 707-731. -[3] I.F. Isakov, V.N. Kolodii. MIS. Opekounov. V.M. Matvienko, S.A. Pechenkin, GE. Remnev. Yu.P. Usov, Vacuum 42 (1991) 159-162. [4] A.D. Pogrebnjak, I.F. Isakov, MS. Opekounov. Sh.M. Ruzimov. A.E. Ligachev, A.V. Nesmelov, I.B. Kurakin, Phps. Lett. A 123 (8) (1987) 410-412. l51 V.V. Vasilvev. E.I. Luconin. E.G. Furman. Priborv i Tekhnika Eksperimenta. no. 6, 1988, pp. 99-102 (in Russian). [6] I.F. Isakov. E.I. Logathev, MS. Opekounov. S.A. Pechenkin. G.E. Remnev, Yu,P. Usov, Pribory i Tekhnika Eksperimenta, no. -3~987,1101--1T)3(InR~~~~~~~~~ ~~ ~ [7] E.I. Logathev, G.E. Remnev, Yu.P. Usov, Pisma v J Techn. Phys. 6 (1980) 1304-1406 (in Russian). [8] G.E. Remnev. M.S. Opekounov, A.N. Grishin. I.V. Ivonin, Radiat. Measurements 25 (l-4) (1995) 739-730. [9] A.D. Pogrebnyak. G.E. Remnev, S.A. Chistyakov, A.E. Ligachev, Izvestiya VUZ’ov, Fizika 1 (1987) 52-65 (in Russian). [IO] Yu.R. Bykovsky, V.N. Nevolin, V.Yu. Fominskii, Ion and Laser Implantation of Metal Materials. Energoatomizdat, Moscow, 1991, p, 240. [ 1l] V.M. Bystritskii, A.N. Didenko, High-intensity Ion Beams, Energoatomizdat, Moscow. 1984, p. 52 (in Russian). [12] E.I. Logathev, G.E. Remnev, Yu.P. Usov, P&ory i Tekhnika Eksperimenta. no. 1. 1983. pp. 21-23 (in Russian). [13] D.R. Akerman. I.F. Isakov. V.N. Kolodii. MSOpekounov, G.E. Remnev, “TEMP” high power ion beams accelerator (Abstract). 1st All-Union Conference, Modification of the Properties of Design Materials by Charged Particle Beams, Tomsk, 1988, Part 1. pp. 34.