Chapter 3
Experiment
The objective of the experiment presented in this thesis is to perform direct detection
of magnetic monopoles in Dy 2 Ti 2 O 7 . This could be achieved by optimizing the
sensitivity of detector to flux noise from a plethora of monopoles anticipated to
be present in mm-sized samples of Dy 2 Ti 2 O 7 in the temperature range of 1K-4K.
To be able to detect noise coming from monopole motion alone, it was important
to eliminate all other sources of noise from entering the detector. To that effect, a
custom cryostat was built to house the spectrometer. This chapter details the design
of a 1K cryostat and the apparatus that houses the Dysprosium Titanate sample that
comprise the Spin Noise Spectrometer. Initial observations of flux noise observed in
our experiment and the premise for Monte Carlo simulations of spin fluctuations in
Dysprosium Titanate are also presented. Finally, a new paradigm for understanding
magnetic monopoles: generation recombination noise is introduced.
3.1 1K Cryostat
The operation of a 1K cryostat is based on the concept of evaporative cooling
which has been known to mankind since time immemorial. The boiling point of liq.
Helium is ∼ 4.2K and pumping on this liquid in a closed system reduces its boiling
point. Cooling of the experiment is done in different stages. First, the experimental
apparatus consisting of a vacuum chamber is brought down to 4K by placing the
vacuum can (VC) in a bath of liquid helium. Then a capillary continuously brings
in a small volume of liquid helium from the bath to a copper pot inside the VC.
Once the pot fills up with liquid helium, it is pumped upon via a stainless steel tube
with diameter 3/4 in. This pumping lowers the temperature of the pot and connected
experiment down to ≈1.2K. The volume of the pot has been optimized to be 25
cm 3 , A schematic diagram of the 1K cryostat in operation is shown in Fig. 3.1. The
© Springer Nature Switzerland AG 2021
R. Dusad, Magnetic Monopole Noise, Springer Theses,
https://doi.org/10.1007/978-3-030-58193-0_3
21
Experiment
The objective of the experiment presented in this thesis is to perform direct detection
of magnetic monopoles in Dy 2 Ti 2 O 7 . This could be achieved by optimizing the
sensitivity of detector to flux noise from a plethora of monopoles anticipated to
be present in mm-sized samples of Dy 2 Ti 2 O 7 in the temperature range of 1K-4K.
To be able to detect noise coming from monopole motion alone, it was important
to eliminate all other sources of noise from entering the detector. To that effect, a
custom cryostat was built to house the spectrometer. This chapter details the design
of a 1K cryostat and the apparatus that houses the Dysprosium Titanate sample that
comprise the Spin Noise Spectrometer. Initial observations of flux noise observed in
our experiment and the premise for Monte Carlo simulations of spin fluctuations in
Dysprosium Titanate are also presented. Finally, a new paradigm for understanding
magnetic monopoles: generation recombination noise is introduced.
3.1 1K Cryostat
The operation of a 1K cryostat is based on the concept of evaporative cooling
which has been known to mankind since time immemorial. The boiling point of liq.
Helium is ∼ 4.2K and pumping on this liquid in a closed system reduces its boiling
point. Cooling of the experiment is done in different stages. First, the experimental
apparatus consisting of a vacuum chamber is brought down to 4K by placing the
vacuum can (VC) in a bath of liquid helium. Then a capillary continuously brings
in a small volume of liquid helium from the bath to a copper pot inside the VC.
Once the pot fills up with liquid helium, it is pumped upon via a stainless steel tube
with diameter 3/4 in. This pumping lowers the temperature of the pot and connected
experiment down to ≈1.2K. The volume of the pot has been optimized to be 25
cm 3 , A schematic diagram of the 1K cryostat in operation is shown in Fig. 3.1. The
© Springer Nature Switzerland AG 2021
R. Dusad, Magnetic Monopole Noise, Springer Theses,
https://doi.org/10.1007/978-3-030-58193-0_3
21