diff --git a/src/pg_rad/data/angular_efficiencies/LU_HPGe_90.csv b/src/pg_rad/data/angular_efficiencies/LU_HPGe_90.csv
new file mode 100644
index 0000000..e71ec6d
--- /dev/null
+++ b/src/pg_rad/data/angular_efficiencies/LU_HPGe_90.csv
@@ -0,0 +1,37 @@
+angle,662,1173,1332
+0,0.015,0.030,0.033
+10,0.011,0.021,0.024
+20,0.086,0.127,0.146
+30,0.294,0.356,0.397
+40,0.661,0.700,0.734
+50,1.054,1.057,1.057
+60,1.154,1.140,1.137
+70,1.186,1.152,1.138
+80,1.151,1.114,1.097
+90,1.000,1.000,1.000
+100,1.020,1.040,1.047
+110,1.074,1.093,1.103
+120,1.113,1.092,1.102
+130,1.139,1.122,1.113
+140,1.146,1.152,1.140
+150,1.113,1.118,1.104
+160,1.113,1.096,1.099
+170,1.091,1.076,1.083
+180,1.076,1.066,1.078
+-170,1.102,1.091,1.093
+-160,1.122,1.100,1.102
+-150,1.128,1.105,1.093
+-140,1.144,1.112,1.123
+-130,1.140,1.117,1.095
+-120,1.146,1.127,1.098
+-110,1.068,1.068,1.045
+-100,1.013,1.025,1.016
+-90,1.004,1.018,1.021
+-80,1.150,1.137,1.132
+-70,1.184,1.167,1.164
+-60,1.158,1.140,1.138
+-50,1.090,1.068,1.064
+-40,0.595,0.620,0.631
+-30,0.332,0.430,0.430
+-20,0.055,0.081,0.096
+-10,0.009,0.018,0.019
\ No newline at end of file
diff --git a/src/pg_rad/data/detectors.csv b/src/pg_rad/data/detectors.csv
new file mode 100644
index 0000000..f5ae726
--- /dev/null
+++ b/src/pg_rad/data/detectors.csv
@@ -0,0 +1,4 @@
+name,type,is_isotropic
+dummy,NaI,true
+LU_NaI_3inch,NaI,true
+LU_HPGe_90,HPGe,false
\ No newline at end of file
diff --git a/src/pg_rad/data/field_efficiencies/LU_HPGe_90.csv b/src/pg_rad/data/field_efficiencies/LU_HPGe_90.csv
new file mode 100644
index 0000000..c94f571
--- /dev/null
+++ b/src/pg_rad/data/field_efficiencies/LU_HPGe_90.csv
@@ -0,0 +1,17 @@
+energy_keV,field_efficiency_m2,uncertainty
+59.5,0.00140,0.00005
+81.0,0.00310,0.00010
+122.1,0.00420,0.00013
+136.5,0.00428,0.00017
+160.6,0.00426,0.00030
+223.2,0.00418,0.00024
+276.4,0.00383,0.00012
+302.9,0.00370,0.00012
+356.0,0.00338,0.00010
+383.8,0.00323,0.00010
+511.0,0.00276,0.00008
+661.7,0.00241,0.00007
+834.8,0.00214,0.00007
+1173.2,0.00179,0.00005
+1274.5,0.00168,0.00005
+1332.5,0.00166,0.00005
\ No newline at end of file
diff --git a/src/pg_rad/data/field_efficiencies/LU_NaI_3inch.csv b/src/pg_rad/data/field_efficiencies/LU_NaI_3inch.csv
new file mode 100644
index 0000000..e3f4b1f
--- /dev/null
+++ b/src/pg_rad/data/field_efficiencies/LU_NaI_3inch.csv
@@ -0,0 +1,64 @@
+energy_keV,field_efficiency_m2
+10,5.50129E-09
+11.22018454,2.88553E-07
+12.58925412,4.81878E-06
+14.12537545,3.55112E-05
+15.84893192,0.000146367
+17.7827941,0.000397029
+19.95262315,0.000803336
+22.38721139,0.00131657
+25.11886432,0.001862377
+28.18382931,0.002373449
+31.6227766,0.002811046
+33.164,0.00269554
+33.164,0.002698792
+35.48133892,0.002509993
+39.81071706,0.002801304
+44.66835922,0.003015877
+50.11872336,0.003227431
+56.23413252,0.00341077
+63.09573445,0.003562051
+70.79457844,0.00368852
+79.43282347,0.003788875
+89,0.003867423
+100,0.003925025
+112.2018454,0.003967222
+125.8925412,0.003991551
+141.2537545,0.004000729
+158.4893192,0.003993145
+177.827941,0.003969163
+199.5262315,0.003925289
+223.8721139,0.003856247
+251.1886432,0.00375596
+281.8382931,0.003619634
+316.227766,0.003446087
+354.8133892,0.003242691
+398.1071706,0.003021761
+446.6835922,0.002791816
+501.1872336,0.002568349
+562.3413252,0.002350052
+630.9573445,0.002147662
+707.9457844,0.001957893
+794.3282347,0.001785694
+891,0.001626634
+1000,0.001482571
+1122.018454,0.00135047
+1258.925412,0.001231358
+1412.537545,0.001116695
+1584.893192,0.001011833
+1778.27941,0.000917017
+1995.262315,0.000828435
+2238.721139,0.000746854
+2511.886432,0.000672573
+2818.382931,0.00060493
+3162.27766,0.000544458
+3548.133892,0.000488446
+3981.071706,0.000438438
+4466.835922,0.000392416
+5011.872336,0.00035092
+5623.413252,0.000313959
+6309.573445,0.000279409
+7079.457844,0.000247794
+7943.282347,0.000218768
+8913,0.000190209
+10000,0.000164309
\ No newline at end of file
diff --git a/src/pg_rad/data/field_efficiencies/dummy.csv b/src/pg_rad/data/field_efficiencies/dummy.csv
new file mode 100644
index 0000000..bd40665
--- /dev/null
+++ b/src/pg_rad/data/field_efficiencies/dummy.csv
@@ -0,0 +1,3 @@
+energy_keV,field_efficiency_m2
+0,1.0
+10000,1.0
\ No newline at end of file
diff --git a/src/pg_rad/detector/builder.py b/src/pg_rad/detector/builder.py
deleted file mode 100644
index 940a2f9..0000000
--- a/src/pg_rad/detector/builder.py
+++ /dev/null
@@ -1,20 +0,0 @@
-from pg_rad.inputparser.specs import DetectorSpec
-
-from .detectors import IsotropicDetector, AngularDetector
-
-
-class DetectorBuilder:
-    def __init__(
-        self,
-        detector_spec: DetectorSpec,
-    ):
-        self.detector_spec = detector_spec
-
-    def build(self) -> IsotropicDetector | AngularDetector:
-        if self.detector_spec.is_isotropic:
-            return IsotropicDetector(
-                self.detector_spec.name,
-                self.detector_spec.efficiency
-            )
-        else:
-            raise NotImplementedError("Angular detector not supported yet.")
diff --git a/src/pg_rad/detector/detector.py b/src/pg_rad/detector/detector.py
new file mode 100644
index 0000000..89a6101
--- /dev/null
+++ b/src/pg_rad/detector/detector.py
@@ -0,0 +1,43 @@
+from importlib.resources import files
+
+from pandas import read_csv
+
+from pg_rad.utils.interpolators import (
+    get_field_efficiency, get_angular_efficiency
+)
+
+
+class Detector:
+    def __init__(
+        self,
+        name: str,
+        type: str,
+        is_isotropic: bool
+    ):
+        self.name = name
+        self.type = type
+        self.is_isotropic = is_isotropic
+
+    def get_efficiency(self, energy_keV, angle=None):
+        f_eff = get_field_efficiency(self.name, energy_keV)
+
+        if self.is_isotropic or angle is None:
+            return f_eff
+        else:
+            f_eff = get_field_efficiency(self.name, energy_keV)
+            a_eff = get_angular_efficiency(self.name, energy_keV, *angle)
+            return f_eff * a_eff
+
+
+def load_detector(name) -> Detector:
+    csv = files('pg_rad.data').joinpath('detectors.csv')
+    data = read_csv(csv)
+    dets = data['name'].values
+    if name in dets:
+        row = data[data['name'] == name].iloc[0]
+        return Detector(row['name'], row['type'], row['is_isotropic'])
+    else:
+        raise NotImplementedError(
+            f"Detector with name '{name}' not in detector library. Available:"
+            f"{', '.join(dets)}"
+        )
diff --git a/src/pg_rad/detector/detectors.py b/src/pg_rad/detector/detectors.py
deleted file mode 100644
index 439ee56..0000000
--- a/src/pg_rad/detector/detectors.py
+++ /dev/null
@@ -1,38 +0,0 @@
-from abc import ABC
-
-
-class BaseDetector(ABC):
-    def __init__(
-        self,
-        name: str,
-        efficiency: float
-    ):
-        self.name = name
-        self.efficiency = efficiency
-
-    def get_efficiency(self):
-        pass
-
-
-class IsotropicDetector(BaseDetector):
-    def __init__(
-        self,
-        name: str,
-        efficiency: float,
-    ):
-        super().__init__(name, efficiency)
-
-    def get_efficiency(self, energy):
-        return self.efficiency
-
-
-class AngularDetector(BaseDetector):
-    def __init__(
-        self,
-        name: str,
-        efficiency: float
-    ):
-        super().__init__(name, efficiency)
-
-    def get_efficiency(self, angle, energy):
-        pass
diff --git a/src/pg_rad/inputparser/parser.py b/src/pg_rad/inputparser/parser.py
index c6dc8b2..9f4d981 100644
--- a/src/pg_rad/inputparser/parser.py
+++ b/src/pg_rad/inputparser/parser.py
@@ -353,41 +353,11 @@ class ConfigParser:
         return specs
 
     def _parse_detector(self) -> DetectorSpec:
-        det_dict = self.config.get("detector")
-        required = {"name", "is_isotropic"}
-        if not isinstance(det_dict, dict):
-            raise InvalidConfigValueError(
-                "detector is not specified correctly. Must contain at least"
-                f"the subkeys {required}"
-                )
+        det_name = self.config.get("detector")
+        if not det_name:
+            raise MissingConfigKeyError("detector")
 
-        missing = required - det_dict.keys()
-        if missing:
-            raise MissingConfigKeyError("detector", missing)
-
-        name = det_dict.get("name")
-        is_isotropic = det_dict.get("is_isotropic")
-        eff = det_dict.get("efficiency")
-
-        default_detectors = defaults.DETECTOR_EFFICIENCIES
-
-        if name in default_detectors.keys() and not eff:
-            eff = default_detectors[name]
-        elif eff:
-            pass
-        else:
-            raise InvalidConfigValueError(
-                f"The detector {name} not found in library. Either "
-                f"specify {name}.efficiency or "
-                "choose a detector from the following list: "
-                f"{default_detectors.keys()}."
-            )
-
-        return DetectorSpec(
-            name=name,
-            efficiency=eff,
-            is_isotropic=is_isotropic
-        )
+        return DetectorSpec(name=det_name)
 
     def _warn_unknown_keys(self, section: str, provided: set, allowed: set):
         unknown = provided - allowed
diff --git a/src/pg_rad/inputparser/specs.py b/src/pg_rad/inputparser/specs.py
index db00bae..be3cd00 100644
--- a/src/pg_rad/inputparser/specs.py
+++ b/src/pg_rad/inputparser/specs.py
@@ -67,8 +67,6 @@ class RelativePointSourceSpec(PointSourceSpec):
 @dataclass
 class DetectorSpec:
     name: str
-    efficiency: float
-    is_isotropic: bool
 
 
 @dataclass
diff --git a/src/pg_rad/utils/interpolators.py b/src/pg_rad/utils/interpolators.py
new file mode 100644
index 0000000..d07bd9c
--- /dev/null
+++ b/src/pg_rad/utils/interpolators.py
@@ -0,0 +1,56 @@
+from importlib.resources import files
+
+import numpy as np
+from pandas import read_csv
+from scipy.interpolate import interp1d, CubicSpline
+
+from pg_rad.configs.filepaths import ATTENUATION_TABLE
+
+
+def get_mass_attenuation_coeff(*args) -> float:
+    csv = files('pg_rad.data').joinpath(ATTENUATION_TABLE)
+    data = read_csv(csv)
+    x = data["energy_mev"].to_numpy()
+    y = data["mu"].to_numpy()
+    f = interp1d(x, y)
+    return f(*args)
+
+
+def get_field_efficiency(name: str, energy_keV: float) -> float:
+    csv = files('pg_rad.data.field_efficiencies').joinpath(name+'.csv')
+    data = read_csv(csv)
+    data = data.groupby("energy_keV", as_index=False).mean()
+    x = data["energy_keV"].to_numpy()
+    y = data["field_efficiency_m2"].to_numpy()
+    f = CubicSpline(x, y)
+    return f(energy_keV)
+
+
+def get_angular_efficiency(name: str, energy_keV: float, *angle: float):
+    csv = files('pg_rad.data.angular_efficiencies').joinpath(name+'.csv')
+    data = read_csv(csv)
+
+    # check all energies at which angular eff. is available for this detector.
+    # this is done within 1% tolerance
+    energy_cols = [col for col in data.columns if col != "angle"]
+    energies = np.array([float(col) for col in energy_cols])
+    rel_diff = np.abs(energies - energy_keV) / energies
+    match_idx = np.where(rel_diff <= 0.01)[0]
+
+    if len(match_idx) == 0:
+        raise NotImplementedError(
+            f"No angular efficiency defined for {energy_keV} keV "
+            f"in detector '{name}'. Available: {energies}"
+        )
+
+    best_idx = match_idx[np.argmin(rel_diff[match_idx])]
+    selected_energy_col = energy_cols[best_idx]
+
+    x = data["angle"].to_numpy()
+    y = data[selected_energy_col].to_numpy()
+    idx = np.argsort(x)
+    x = x[idx]
+    y = y[idx]
+    f = interp1d(x, y)
+
+    return f(angle)