1 Introduction

Conventionally, the relevant energy range for measuring Mössbauer spectra is limited with thresholds [1]. This requires the setting of these before the measurement. When changing the detector system, or when changing the observed energy range, a calibration measurement for the thresholds is required. Furthermore, classically only one energy range is investigated [1]. With our two dimensional (2D) approach, not only the photons from a previously defined energy range are measured, but all photons are stored with their respective energy and the velocity of the Mössbauer drive [2]. From the resulting 2D spectrum, the Mössbauer spectrum can then be obtained after the measurement. In the case of the iron-57, the spectra of the 6.4 keV and 14.4 keV (classical) can be obtained in parallel, see Fig. 1. Since an energy spectrum is also recorded for each measurement, it would be possible to use the evaluation unit with a suitable excitation source for X ray fluorescence measurements.

Fig. 1
figure 1

Example 2D spectrum with extracted energy and Mössbauer spectra

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2 Measurement Setup and Results

2.1 Old Setup

A schematic overview of the previous measurement setup is shown in Fig. 2. For example, our processing unit can be operated with a gas detector setup (proportional counter + shaper-amplifier) from the “WissEl” company and can also provide the triangular signal for a “WissEl” drive unit. Each component requires its own power supply. Until now, the MIMOS detector [3] could also be used with our processing unit but only with an additional external power supply.

Fig. 2
figure 2

Previous schematic measurement setup of our processing unit

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2.2 New setup

The experimental setup was expanded with a separate power supply for a MIMOS drive [3] and a MIMOS detector, so that it is now possible to measure directly with the processing unit without a separate power supply. The schematic measurement setup is shown in Fig. 3.

Fig. 3
figure 3

Schematic measurement setup of the new processing unit in combination with MIMOS drive and MIMOS detector

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This results in a compact transmission measurement setup. A picture of the setup is shown in Fig. 4. In the upper part, the MIMOS drive and MIMOS detector can be seen below the new processing unit.

Fig. 4
figure 4

Picture of the compact transmission setup with the new processing unit (green marked) in combination with MIMOS drive (blue marked) and MIMOS detector (orange marked)

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The setup was tested by measuring an α-iron foil (0.02 mm) with a cobalt-57 source in a rhodium matrix at 293 K. It was measured for 24 h. Then, the Mössbauer spectra in the energy ranges of 6.4 keV (1) and 14.4 keV (2) were extracted from the energy spectrum shown in Fig. 5.

Fig. 5
figure 5

Energy spectrum of the test measurement (setup from Fig. 3) with the marked energy regions 6.4 keV (1) and 14.4 keV (2)

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Afterwards, the Mössbauer spectra were calibrated, folded and fitted (lorentzian site analysis) with the program „Recoil “. The resulting Mössbauer spectra with fits are shown in Fig. 6.

Fig. 6
figure 6

Mössbauer spectra with fits of the test measurement (setup from Fig. 3) from the energy regions 6.4 keV (left) and 14.4 keV (right)

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The Mössbauer parameters [1] for the 6.4 keV | 14.4 keV spectra of the fits are as follows:

  • Center Shift CS = -0.0001(61) | 0.00065(90) mm/s

  • Quadrupole Splitting QS = 0.0004(61) | -0.00016(90) mm/s

  • Magnetic Splitting MS = 32.973(49) | 32.9653(72) T

  • Area A = -21000(1100) | 143600(1100) counts·mm/s

  • Half Width at Half Maximum w3 = 0.144(23) | 0.1369(34) mm/s

  • A1/A3 = 2.48(30) | 2.501(46)

  • A2/A3 = 1.87(24) | 1.790(36)

  • w1/w3 = 1.27(21) | 1.273(33)

  • w2/w3 = 1.06(19) | 1.114(31)

The fits show the expected values. The CS and QS should be 0.00 mm/s for α-iron. [1] The MS should be around 33.0 T at 298 K [4]. Smaller deviations can be explained by material differences. The natural half width at half maximum is 0.098 mm/s. Depending on the sample and the setup, the values are slightly higher. The signal ratio for optimal absorber thickness is 3–2-1. The ratios are slightly smaller, which may be due to the thickness of the iron foil [1].

With the processing unit it is now also easily possible to combine the MIMOS drive with another detector system, for example with a silicon drift detector (SDD). A SDD has a much better energy resolution so the 6.4 keV and 14.4 keV energy regions can be better separated. The amplified and shaped signal of the SDD is fed directly to the board. The voltage supply of the SDD and the shaper are then external again. The schematic setup with the SDD is shown in Fig. 7.

Fig. 7
figure 7

Schematic measurement setup of the new processing unit in combination with MIMOS drive and a silicon drift detector (SDD)

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The setup was also tested by measuring an α-iron foil (0.02 mm) with a cobalt-57 source in a rhodium matrix at 293 K. It was measured for 24 h. Then, the Mössbauer spectra in the energy ranges of 6.4 keV (1) and 14.4 keV (2) were extracted from the energy spectrum shown in Fig. 8.

Fig. 8
figure 8

Energy spectrum of the test measurement (MIMOS drive + SDD, setup from Fig. 7) with the marked energy regions 6.4 keV (1) and 14.4 keV (2)

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Afterwards, the Mössbauer spectra were calibrated, folded and fitted (lorentzian site analysis) with the program “Recoil”. The resulting Mössbauer spectra with fits are shown in Fig. 9.

Fig. 9
figure 9

Mössbauer spectra with fits of the test measurement (MIMOS drive + SDD, setup from Fig. 7) from the energy regions 6.4 keV (left) and 14.4 keV (right)

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The Mössbauer parameters [1] for the 6.4 keV | 14.4 keV spectra of the fits are as follows:

  • Center Shift CS = 0.0008(11) | -0.00007(56) mm/s

  • Quadrupole Splitting QS = -0.0006(11) | -0.00019(56) mm/s

  • Magnetic Splitting MS = 32.9455(85) | 32.9479(42) T

  • Area A = -123100(1200) | 191400(1000) counts·mm/s

  • Half Width at Half Maximum w3 = 0.1348(44) | 0.1314(24) mm/s

  • A1/A3 = 2.513(62) | 2.516(34)

  • A2/A3 = 1.787(48) | 1.787(26)

  • w1/w3 = 1.134(39) | 1.123(21)

  • w2/w3 = 1.076(41) | 1.061(22)

The fits show the expected values. The CS and QS should be 0.00 mm/s for α-iron. [1] The MS should be around 33.0 T at 298 K [4]. Smaller deviations can be explained by material differences. The natural half width at half maximum is 0.098 mm/s. Depending on the sample and the setup, the values are slightly higher. The signal ratio for optimal absorber thickness is 3–2-1. The ratios are slightly smaller, which may be due to the thickness of the iron foil [1].

Furthermore, it is now possible to use the MIMOS detector directly with another drive, for example a „WissEl “ drive, since a separate power supply for the detector is no longer required. The schematic setup with the SDD is shown in Fig. 10.

Fig. 10
figure 10

Schematic measurement setup of the new processing unit in combination with „WissEl “ drive and a MIMOS detector

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The setup was also tested by measuring an α-iron foil (0.02 mm) with a cobalt-57 source in a rhodium matrix at 293 K. It was measured for 24 h. Then, the Mössbauer spectra in the energy ranges of 6.4 keV (1) and 14.4 keV (2) were extracted from the energy spectrum shown in Fig. 11.

Fig. 11
figure 11

Energy spectrum of the test measurement (WissEL drive + MIMOS detector, setup from Fig. 10) with the marked energy regions 6.4 keV (1) and 14.4 keV (2)

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Afterwards, the Mössbauer spectra were calibrated, folded and fitted (lorentzian site analysis) with the program „Recoil “. The resulting Mössbauer spectra with fits are shown in Fig. 12.

Fig. 12
figure 12

Mössbauer spectra with fits of the test measurement (WissEL drive + MIMOS detector, setup from Fig. 10) from the energy regions 6.4 keV (left) and 14.4 keV (right)

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The Mössbauer parameters [1] for the 6.4 keV | 14.4 keV spectra of the fits are as follows:

  • Center Shift CS = 0.0026(45) | 0.0004(10) mm/s

  • Quadrupole Splitting QS = 0.0011(45) |—0.0008(10) mm/s

  • Magnetic Splitting MS = 32.927(34) | 32.9504(77) T

  • Area A = -23340(960) | 130900(1200) counts·mm/s

  • Half Width at Half Maximum w3 = 0.143(19) | 0.1620(44) mm/s

  • A1/A3 = 2.76(27) | 2.431(50)

  • A2/A3 = 1.98(21) | 1.745(39)

  • w1/w3 = 1.19(16) | 1.076(31)

  • w2/w3 = 1.13(16) | 1.025(32)

The fits show the expected values. The CS and QS should be 0.00 mm/s for α-iron. [1] The MS should be around 33.0 T at 298 K [4]. Smaller deviations can be explained by material differences. The natural half width at half maximum is 0.098 mm/s. Depending on the sample and the setup, the values are slightly higher. The signal ratio for optimal absorber thickness is 3–2-1. The ratios are slightly smaller, which may be due to the thickness of the iron foil [1].

3 Conclusion

By upgrading our 2D processing unit with a power supply for a MIMOS detector and MIMOS drive, we have obtained a very small and at the same time flexible transmission measurement setup. The setup can be used with MIMOS detector and e.g. „WissEl “ drive, as well as with MIMOS drive and e.g. silicon drift detector or gas detector.